The Instruments Ken Griffin Played
Eric C. Larson
Ken's Electrostatic Wurlitzers
As this website admirably demonstrates, Ken Griffin was one of America's most popular entertainers, and perhaps the most widely known American organist. Although there is much information about Ken, the man, and his playing, I will address an entirely different aspect of Ken's music; the instruments he played.
To say that Ken's playing is distinctive is an understatement. Although seemingly simple, his unique sounds are extremely difficult to copy accurately. Many people have tried to imitate Ken Griffin, and although many musicians can play more elaborate arrangements, Ken's direct, straight-forward playing is a real challenge for anyone to copy. Most who try to do so ultimately sound not like Ken, but like people trying to sound like Ken Griffin. To imitate Ken successfully requires a surprisingly good and accurate keyboard technique, and even more importantly, it also requires the specific instruments which he used, along with some interesting auxiliary equipment and some specialized recording techniques.
Although I have not heard every single recording that Ken Griffin made, it seems safe to say that the major portion of his work was done on two instruments of his era, the tonewheel Hammond organ, and the electrostatic Wurlitzer organ. Although the Hammond is widely known, and indeed Ken did most of his work on the Hammond, he also used the electrostatic Wurlitzer for perhaps ten to fifteen percent of his musical output, including one entire LP record, 67 Melody Lane. The Wurlitzer electrostatic organ was also the instrument which he used on his TV show by the same name.
It is not my intention to delve in detail into esoteric electric or electronic or musical principles and theory here, but there are a few basic concepts which are really helpful to understand. I will assume that those of you reading this have at least a cursory knowledge of the organ as a musical instrument, both pipe and electronic.
One key concept to understand is that any soundwave can be converted into an analog electrical equivalent wave, and that such an electrical wave is always an alternating current. It is also necessary to realize that many different, various frequency alternating currents representing, for example, all the instrument sounds of a big symphony orchestra (or all the notes of multi-note chords and multiple stops on an electronic or pipe organ) can be combined into a single, complex alternating current.
This complex current accurately conveys all of the individual tones, timbres and pitches of the orchestra or organ to a speaker through a single circuit consisting of only two wires. (Four if two-channel stereo.) Furthermore, since this complex signal is alternating current, we can step it up or down with transformers, we can make it flow around in capacitive circuits, and it can transmit power. We can also amplify, attenuate, and phase-shift it just like industry does with standard alternating current power.
Most circuits, components and systems in both electronic organs and also stereo and hi-fi analog and digital music systems use unidirectional or direct current for their operation. It is, therefore, not only possible but commonplace to find both a DC operating voltage and also an AC audio signal voltage present in the same circuit, wire or component as we shall soon see.
What a particular musical tone sounds like to us as listeners depends on the presence or absence of particular harmonics and also non-harmonic partials in the actual soundwave. A harmonic is a pure tone whose frequency is an integral multiple of the frequency of the basic musical tone in question. A partial is similar, but its frequency is not an integral multiple of the musical tone of interest. A second important determinant of the sound of a musical tone is the way in which it begins and ends.
For instance, a note on a piano begins loudly very suddenly, drops fairly quickly at first, then continues to fade away gradually. There is also a soft but audible "clack" or slight thud just as the hammer first contacts the one, two, or three strings for a particular note. The tone of many higher piano tones is not too different from the higher tones of a flute, but a flute's tone starts only moderately quickly and likewise stops moderately quickly, and while sounding, maintains a fairly uniform volume. There may also be a slight "chirp" or chiff right at the beginning of some flute tones.
The tonal impressions that we get from the higher pitches of a flute, and the higher notes on a piano are therefore completely different to us and we have no difficulty differentiating them. Still another aspect is the presence of transients, or short duration extra harmonics, partials or even extraneous noises that usually occur at the onset of a musical tone. [The chiff at the onset of some flute notes, and the hammer noise of a piano are good examples of this.] Various electronic organs may simulate some or all of these characteristics to provide facsimiles of different instrument sounds. Modern digital synthesizers reproduce these effects extremely accurately.
Vibrato is a periodic and regularly occurring wavering in a musical tone. It is present in the voices of all good singers, and many musicians incorporate it into their instrument playing as well. Vibrato is actually a slight changing of the instantaneous pitch of a musical tone, done so that the pitch varies smoothly both a little above and below the intended pitch. The average pitch over time remains unchanged; but the instantaneous pitch is constantly changing.
Tremolo is a periodic and regularly occurring variation in the loudness of a musical tone, without any change in pitch. Of the two effects, vibrato is far more appealing and desirable. Both vibrato and tremolo may occur simultaneously, and both sound best when they occur between 360 to 420 times per minute, or 6 to 7 times per second.
Celesting or chorusing is a subtle, gentle wavering or undulation which sometimes creates the illusion of motion in musical tones and occurs when two or more tones having very nearly (but not exactly) the same frequencies sound together. In some modern digital electronic instruments the maker may use the term "ambience" or "ensemble" for this effect. Such an effect adds life and richness to music, and is present in virtually all situations where a number of singers or musicians perform together. It is also present in most polyphonic musical instruments. Pianos, with their three-strings-per-note for all midrange and higher notes are another good example of this.
To be successful, celesting or chorusing frequencies must be very close in pitch. If the pitch difference exceeds a certain somewhat subjective point, the individual tones begin to sound out-of-tune with each other, which in fact they are. The degree of out-of-tuneness which is tolerable is frequency dependent. As frequencies become higher pitched, the differences between them become smaller and smaller in order to produce acceptable chorusing or celesting without sounding out-of-tune.
Phasing of electrical or soundwaves refers to where they are at any instant over time with reference to a starting position, or to each other. The best way to illustrate phase is by means of a simple diagram, which shows three identical soundwaves of the same pitch, amplitude(loudness) and timbre. In this case, we will use simple sine waves to illustrate the concept of phase. In the diagram, we have referenced the waves to a circle. The red wave starts at our zero reference at the intersection of the horizontal (time) and vertical (amplitude) axes.
Notice that the green wave has already reached its positive maximum when the red wave is just starting. By referring to the circle at the left, we see that the dotted line goes to the +90º position. We therefore say that in this diagram, the green wave is 90 degrees out of phase with the red wave, and that its phase is leading, because in time, it is ahead of the red wave.
Likewise, the blue wave is still returning from the negative side of the base line and doesn’t reach the (zero) starting point until the red wave has already reached its positive peak and is starting to decrease. Therefore, referring to the circle again, we see that the blue wave is 90 degrees out of phase with the red wave, and its phase is lagging, because in time, it is following behind the red wave. Likewise, we see that the difference or span between +90º and –90º is 180º and therefore in this diagram the green and blue waves are 180º out of phase with each other. Phase difference is typically expressed by degrees, which the reference to the circle makes very easy to see. Phase difference can be any whole or fractional number of degrees lagging or leading. I chose to use ninety degrees here to make the example easy to understand, and easy for me to draw!
When a wave gradually either advances or retards in phase in real time, this changing of phase is also accompanied by a change in frequency. If a wave undergoes a full 360º phase change in one second, there will be a frequency shift of one cycle per second. If the wave advances in phase, the frequency will increase by one cycle per second. If the wave retards in phase, there will be a decrease of one cycle per second. Likewise, if, for example, the wave changes by 3600º in one second, (ten times around the circle) there will be a ten cycles per second change in frequency. This frequency change occurs only while the phase of the wave is changing. As soon as the wave stops changing in phase, the frequency will once again be whatever it was before.
This concept of real-time phase changing and resulting frequency change is very important when we consider the means in which both the Hammond organ and also the Wurlitzer organ produce their respective vibrato effects. Both instruments use continuous phase changing (both lagging and leading) to create their pitch-varying vibratos.
There were essentially two operating principles for electronic organs of Ken's time; keyed-audio, and keyed-generators. In the first category of keyed-audio there are two sub-categories, that of direct-keyed audio and electronically-keyed audio. All electronic organ tones, regardless of the operating principle, originate in an assembly known as a tone generator, essentially a device for generating or providing numerous alternating currents whose frequencies are those of the individual keys and pedals of the instrument. In either type of keyed-audio system, the alternating currents representing the audio or actual tones are available as long as the instrument is turned on. The keys and pedals then switch the appropriate audio AC voltages to the voicing circuitry and ultimately to the amplifiers and speakers of the instrument.
In a direct-keyed audio system, the audio signal voltages are present on the actual key and pedal switch contact assemblies. In the electronically keyed audio system, the audio signals are present at the inputs of keying or gating circuits. The gating circuits are controlled by the key contacts of the manuals and pedals of the instrument.
In the keyed-generator system, the tone generators are normally inoperative, and will only produce their audio AC voltages when they are turned on, or keyed, usually with a DC voltage, by the playing keys and pedals of the instrument. The Hammond tonewheel organs of Ken's time operate on the direct keyed-audio system, and the electrostatic Wurlitzer organs are keyed-generator instruments. Many of the more modern electronic organs, including the newer, non-tonewheel Hammonds use the electronically-keyed audio system. Also, the touch-response percussion of the B3 is an example of electronically keyed audio.
As we said, the majority of Ken's musical work was played on Hammonds, but we will consider the electrostatic Wurlitzer first. This is the instrument he used exclusively on 67 Melody Lane, both the record album and his TV show by the same name. He also used it on a number of selections on his other recordings, notably September Song, Far Away Places, Love Letters in the Sand, Dream, My Dreams are Getting Better All the Time, I want to Be Happy, Teardrops on My Pillow, Valencia, The Nearness of You, Moonbeams, September in the Rain, Somebody Else is Taking My Place, You Are My Sunshine, Marcheta, and I Don't Want to Set the World on Fire.
In addition to the above, Ken made a series of radio transcription recordings during the early 1950s. I do not know exactly when he made these recordings or how generally they were distributed. They were originally recorded on special very large diameter LP records which cannot be played on ordinary turntables, and I consider myself very fortunate to have been presented with a set of three cassettes which were made from these original special discs. On these radio transcriptions, Ken used the Wurlitzer electrostatic organ for a number of selections. Of the three radio transcription cassettes that I have, the Wurlitzer occupies roughly 70 percent of the total playing time on one of these cassettes. Ken may also have used the Wurlitzer on other recordings, but I do not know this with certainty as I have not yet heard all of Ken Griffin's recordings.
The electrostatic Wurlitzer is a unique and completely different instrument from any other electronic organ. From its very distinctive sounds to its operating principle, it is definitely in a class all by itself. In complete contrast to the wealth of information to be found on the Internet about Hammonds, I have found virtually nothing about these instruments, therefore, I will elaborate significantly on this most unusual electronic organ.
This next picture, figure 2, shows a general view of a Wurlitzer electrostatic organ, and the inset is a closer view of its stop rail, which appears to be very similar to the stop rails of many other electronic organs of the 1950s and 60s. Compare this with several pictures in Bill Reid's listing of the Ken Griffin records that he has. Here you'll see several pictures of the electrostatic Wurlitzer that Ken used on these albums.
I must now preface my remarks with a notice that in many places in this Ken Griffin website, you will see the Wurlitzer instrument referred to by myself and other contributors as the ES organ or Wurlitzer ES. This is simply the abbreviation for the word electrostatic. Also, it is the term we of the Ken website have adopted for the instrument although it is not original with us. These organs were not called or marketed by Wurlitzer as ES organs. We choose to call them that because they operate on the principle of the electrostatic transducer which we will explain shortly. In like manner, we refer to Hammond organs of that era as tonewheel organs, again because of their operating principle.
Wurlitzer's actual model designations for these organs, which were built in the period from roughly 1946 to 1961, were the 4400 series, 4600 series, and 4800 series instruments. Ken, as far as we know, used various 4601 models. The one which I have used for some of my Ken Griffin imitations, and from which these and subsequent pictures were taken is a model 4602. The 4400 series are spinets, of which the 4410 and 4450 were sold in relatively large numbers. The 4800 series models are thirty-two pedal concert organs with liturgical voicing and stop nomenclature. The 4601 is a 25 pedal console designed for pops playing. The 4602 is a 32 pedal version of the 4601 console with more classical stop nomenclature. The 4601 and 4602 are very similar in general appearance and also internally, but with some differences in stop designation and amplification.
The electrostatic Wurlitzer is sometimes called a Wurlitzer reed organ, or an amplified reed organ. Both of these names are incorrect, however, because they imply that you hear the sound of reeds when you play this instrument; an implication which is absolutely false. It is true, however, that the electrostatic Wurlitzer organs do contain air-powered free reeds, one reed for each available frequency. However, everything possible is done so that the actual sound of the reeds can't be heard. And indeed, this is a very good thing, for in the electrostatic Wurlitzer, all of the 73 or 85 reeds (depending on the model) sound at once; and they sound all the time when the instrument is turned on. A high-speed centrifugal compressor or blower, which is an integral part of the reed unit, powers this system.
In order to understand the electrostatic organ, we need first to learn a little bit about capacitors. In its simplest form, a capacitor is nothing more than two sheets or plates of metal, parallel to and close to each other, but separated by either an air space or else some other insulating material.
If we connect this elementary capacitor to a source of direct current, such as a battery as shown in figure 3, for a very brief instant, current will flow until the plates of the capacitor are fully charged. At this point, no further current will flow, because the plates are separated from each other. If we were to disconnect this capacitor from the power source, we would find that a voltage equal to that of the charging voltage would remain on the plates. Connecting the two plates together would very quickly discharge the capacitor and most likely produce a visible and audible spark.
Now the general equation for capacitors is this: Q = CE, where Q is the electrical charge in Coulombs, C is the capacitance in Farads, and E is the voltage of the power supply. Because this is an equation, both sides must always equal each other, and any change to any term must be balanced by a compensating change on the other side of the equal sign.
The capacitance (how much of an electrical charge it will hold) of a capacitor depends among other things on the physical distance between the plates. If we move the plates closer together, the capacitance increases, and it can hold a bigger charge. Conversely, if we move the plates away from each other, the capacitance decreases and it can not hold as much of a charge as it could previously when the plates were closer together. Of course the surface area also governs the capacitance. For this example, however, let us assume that the plate size is fixed.
Let's now say that we have a certain capacitor, and we have applied a voltage across it from a battery, and the capacitor is fully charged. I appear on the scene and push the plates closer together. (Naturally, I'm wearing my insulated electrical workers' gloves for this venture.) Because the capacitance has increased, more current will flow until the capacitor has taken on a bigger charge. (Holds more electrons.) Now, I decide to see what will happen if I move the plates away from each other. When I do this, C decreases. The equation, however, must always balance. Since the battery has constant voltage, then the charge, Q, must decrease also, and while I am moving the plates apart, current flows from the capacitor back to the battery until a new, smaller charge (fewer electrons) exists which is consistent with the new distance between the plates.
This says to us that if I provide some means of moving the capacitor's plates together and then apart, and do this at, say 440 times per second, then a current will flow into and out of the capacitor, and it will make 440 complete cycles per second. This further tells us that I could perhaps use this changing current to provide a musical tone if I can somehow extract it and put it to work. Therefore, I place a load resistor in the circuit as shown in figure four:
Whenever a current flows through a resistor, a voltage drop will occur across the resistor according to well-established electrical laws. Furthermore, the signal voltage that I can get will be alternating, as the current flows first into and then back out of the capacitor. This AC voltage, however, will in effect be "riding" on the DC voltage that I must apply to this capacitor in the first place to charge it so that it can give us the AC signal. Here is a very good example of both DC and AC coexisting in the same device.
It is also very important to understand that current cannot flow through a capacitor. The two plates are always (by definition) separated from each other; there is no connection between them. Therefore current can only flow into or out of a capacitor, but never through it. If an alternating current exists in a capacitive circuit, then it will flow around in the circuit, into and out of the capacitor, but again, never through it.
Nevertheless, in many ways, an alternating current flowing around in a capacitive circuit behaves as though it were in fact flowing right through the device. This concept is important to keep in mind as we get further into our discussion of the electrostatic Wurlitzer instrument and also the Hammond. For practical purposes in our discussions of and thinking about audio signal applications, we may correctly speak of the AC signals as flowing through capacitors, because they behave exactly as though they did this.
Capacitors, by virtue of the above properties, produce a number of other interesting phenomena, some of which are also utilized in both types of electronic organs. Of course, if we put too high a voltage across the plates of a capacitor, the voltage will cause an arc to form, and then current will jump across and flow, via the arc, from one plate to the other. Current will also truly flow through a capacitor if we cause the plates to touch each other. Both of these are, however, abnormal conditions, and I mention them as such. For the purposes of this discussion, we will assume that the voltage will never be high enough to arc across the plates of any capacitors of any electronic organs, nor will their plates ever touch.
Now then, let's return to a capacitor whose plates can move back and forth at a rapid rate. This implies that if I want, I could use a capacitor whose plates move closer together and then apart 440 times a second to give us an alternating current voltage with a frequency of, you guessed it, standard A440. Furthermore, if I can get enough friends together, and give each of them a capacitor along with specific instructions to move their capacitor plates back and forth at other musical frequencies, I should be able to hook up DC voltages, a load resistor and finally, a 61 note organ keyboard to all of these capacitors and utilize the resulting different frequency AC voltages to drive a speaker and make all the notes of the scale. And this is great. They do the work, and I get to play!
Now, keeping a crew of 61 individuals busy shoving capacitor plates back and forth at rapid rates is somewhat impractical, especially when we'll be zapping them with high voltage direct current each time I choose to press a key! (I, of course, am using a keyboard with plastic keys, so I am insulated from the high voltage DC.)
There is, nevertheless, a very simple device which can serve the purpose, and that is the lowly brass free reed, just like those that you find in the old foot-pump reed organs and in accordions. Reeds are simple, cheap, and, if they are of this so-called free type, such as those in the aforementioned instruments, they are also extremely pitch-stable and reliable.
Free reeds consist of a narrow strip of springy metal such as hard brass, and also a supporting frame or shallot with a suitable opening over which the reed strip vibrates when air flows by the reed and through the opening in the correct direction. In a free reed, the opening in the shallot is very slightly larger than the reed itself, and thus the reed strip vibrates into the opening for part of each cycle. This is why it is called a free reed, since the vibrating portion of the reed strip doesn't touch, or is free of, the supporting shallot. In a typical free reed, the clearance between the reed and the opening into which it vibrates is no more than a few thousandths of an inch. Free reeds, especially the small ones that are used for the high frequencies of a keyboard instrument require a watchmaker's precision in their manufacture and initial tuning.
Anyhow, I can use a vibrating brass free reed as one plate of a capacitor. All I need to do then is to get a second plate, and place it close to the reed, preferably right over it. Now, if I put a DC voltage across the reed and the stationary plate, I have, (wowser, would you believe?) a capacitor with one of its plates moving rapidly back and forth. Put a load resistor in the circuit, and there it is: a simple, stable, and accurate producer of a suitable alternating current that can become one note on a keyboard or a pedal board of an electronic organ.
It is at this point very important to realize that this vibrating 'reed' capacitor does not generate any electricity. It simply modulates the charging voltage which exists across it. The modulation of the charging voltage results in a varying voltage, which when developed across a load resistor and extracted through an isolation or coupling capacitor (to be described in a little while) is then an alternating current audio signal which can be amplified, filtered, phase-shifted, reverberated, sustained or otherwise processed into one note or tone of an electronic organ.
Note also that the charging DC voltage either exists or does not exist on the reed and on the close-proximity stationary plate, however, no direct current ever flows through the reed-capacitor. It is because there is no current flow through, only a charging potential across, that we use the term electrostatic, which by definition means no current flow. In other words, a static electrical charge can exist across the reed-capacitor.
Free reeds produce a characteristic and rather unpleasant sound. You need only listen to an accordion to confirm this. In the Wurlitzer electrostatic organ, however, we're not interested in the sound of the reeds at all. In fact, the direct acoustic sound of the reeds is simply a useless by-product of their operation, and as some of the following pictures and text will show, elaborate measures are taken to insure that we will never hear the actual reed sound from these instruments.
What we are interested in, however, are the possible AC audio voltages which, as one plate of vibrating variable capacitors, these reeds can provide for us. In the electrostatic Wurlitzer, each reed has from one to three separate electrodes called pickups in close proximity. One pickup is over the approximate center of the reed. One is directly above the free end or tip of the reed, and the third is arranged right at the front edge of each reed.
If we put a DC voltage across the reed and any one of the three pickups, then together, they will constitute a small capacitor. Since the reed is vibrating, the capacitance is constantly changing at the reed vibration frequency. When we put a DC voltage across a pickup and the reed, a current must flow into and then out of the resulting reed-capacitor as the reed vibration changes its actual capacitance. This current is, as we already stated, an alternating current, and it has the same frequency as that of the reed. We can then stick a load resistor in series with the reed, and every time we zap any pickup of this reed-capacitor with a DC voltage, we'll get a corresponding AC audio voltage across the resistor.
Free reeds of this type would be very slow in developing their steady state output tones if we were going to use them as direct sources of sound and subsequently keyed the operating air to them. The larger reeds that we would need for organ pedal tones, for example, can take up to two seconds to reach full acoustical output. This would make such a reed impractical for many types of music, especially any music with a decided beat and a rhythmic bass pattern such as the majority of Ken's playing exhibits. This of course was one of the major drawbacks of early reed organs. Furthermore, the tone of free reeds is, as we just mentioned, very unpleasant; snarling and growling at lower frequencies and wheezy and keening at higher frequencies. Again, think of the accordion. There really is a reason for all those accordion jokes!
However, when we use such a reed as a variable capacitor in the Wurlitzer electrostatic organ, we can key it very rapidly, because we're keying the DC voltage to the pickups, and the reed is always in motion. As long as we keep the reed vibrating mechanically, we can key the pickups as fast as we want, and the tone will start and stop instantly. Not only that, we can add circuitry to modify the way in which the keying voltage on the pickups builds up or decays. We can, therefore, use this system to create fast percussive or slow mellow attacks or onsets to the generated tone, and we can also introduce percussion sustain, something impossible on either a reed organ or an accordion.
Another nice feature of this system is that two of the three resulting tones that we get by amplifying the AC audio voltage from the three pickups of these reed-capacitors sound nothing at all like an accordion. Indeed, if we put our pickups over the centers of the reeds, we will get a soft flutelike tone, very similar to that of the pipe organ Melodia or concert flute stop. If we put a pickup above the free, vibrating end of the reed, we get a tone somewhat like that of a diapason. If we then place a third pickup so that it looks at the vibrating front edge of the reed, we get a complex tone with considerable harmonic development which is good for orchestral reed and string voices. This tone does bear a slight resemblance to the sound of an accordion but it is nevertheless quite different and has none of the unpleasantness of accordion sound.
The heart of the Wurlitzer electrostatic organ is its reed unit, a hermetically sealed assembly with a bank of 85 reeds (in the 4600 series console versions) covering the entire pitch range from the low C of the 16 foot pedal stops to the top C of the four-foot flute stops. Here are two views of the interior of the electrostatic Wurlitzer. The first, is a general look inside the console with the back cover removed. It shows the basic layout, and as you can see, it looks like any typical 1950s electronic organ, with a chassis with vacuum tubes at the bottom, and a self-contained speaker in the center. The reed unit is to the right, just barely visible in this picture. The blower motor is visible on the bracket attached to the side of the reed unit.
This next picture shows the reed unit with part of the external soundproofing removed. The centrifugal blower is plainly visible on the top of the reed unit, and you can also see the blower drive shaft extending to the left and out through the side of the soundproof enclosure. The blower motor is the only part of the reed system that is external to the soundproof housing. This photo also shows the top portion of three of the seven reed pans directly below.
All eighty-five reeds blow at once as long as the instrument is operating. The reeds are arranged by octaves inside these pressed-steel pans as shown, one octave to each pan. The pans are lined with eighth-inch thick rubber for sound suppression. Each pan is held in place by three nuts and seats on a gasket, thus making the system hermetically sealed when all pans are in place. The operating air for the reeds is continually recirculated inside the reed unit with no exchange of outside air, thus excluding any dust and dirt from the system. In addition to sealing the reeds from the outside air, the pans, being steel and being grounded through their retaining nuts and threaded rods, also provide electromagnetic and electrostatic shielding which is necessary to keep away power line and radio and TV interference from the reeds' output signals.
The entire reed unit mounts as shown in the soundproof enclosure consisting of an outside box of 1/2" Homasote, followed by one inch thick heavy felt, and 3/16" Masonite. This then gives a total of 5 different layers of material between the reeds and the outside of the reed unit assembly; rubber, steel, Masonite, felt, and Homasote. This next photo, with a little more of the soundproof enclosure removed, shows the other side of the reed unit and the additional seventh pan on the end. It also shows the steel reinforced construction of the soundproofing enclosure.
The centrifugal compressor or blower draws air through the reeds into a chamber behind each group of reeds. The chambers communicate to a central exhaust manifold that connects to the blower intake assembly in which there is a very fine-mesh screen. The discharge of the blower enters the high pressure manifold which feeds the air back into each pan through individual openings fitted with adjustable slides or gates. Since the amount of air withdrawn from each pan through the reeds always equals the amount of air returned to each pan, the interiors of the pans remain effectively at atmospheric pressure. The reeds, therefore, can be said to operate on suction relative to the outside world. The reeds under any pan will continue to operate with a pan removed, which is necessary should the need arise to adjust the pickups on the reeds.
The direct sound of the reeds with a pan removed for servicing, particularly those in the mid-range of the instrument, is really terrible, sounding like a serious accident at the accordion factory. The reeds, however, are very small-scale, because they do not have to produce any acoustic output so it is not unbearably loud. Also, since the reeds vibrate all the time, they are lightly blown so that they do not vibrate through a very large amplitude.
This low amplitude vibration is necessary so that they will not weaken over time and snap off from metal fatigue. The reeds of a reed organ or an accordion, which instruments depend on the actual sound of the reeds for their tones, must of necessity make lots of noise and vibrate at a greater amplitude. Of course in reed organs and accordions, the reeds do not have to vibrate all the time, only when called upon to produce a particular note. This is the main function of the adjustable blast gate in each pan; to limit the total airflow through each group of reeds and keep the mechanical amplitude of vibration minimal. It also keeps each group of reeds vibrating at a consistent level with respect to the other groups, so that no one particular group vibrates too much or too little.
The reeds of the first or sub-octave group have only one pickup, about two thirds of the way towards the free end of each reed. These reeds are used only for notes one through twelve of the pedal 16' stops. This next picture shows a close-up of the pedal 16' reeds.
Other groups of reeds may have either two or three pickups. In various different models of the electrostatic Wurlitzer, the pickups over the centers and the tips of the reeds may have different functions. In some, one pickup is for pedal tone, in another the center pickup may provide a soft, flutelike tone. The pickups over the free ends of the reeds are for the normal manual flute stops, and the pickups at the leading edge of the reed tips generate the so-called trumpet tone, which is a more or less generic reedy tone having considerable harmonic development. The very last or top octave group of reeds, labeled octave number six, generates the top octave of frequencies for the four foot pitch range and has only one pickup per reed. These pickups are considered normal flute tone pickups. This next photo shows the next to the highest octave of reeds, with only two pickups per reed, and as you can see, these treble reeds are extremely small.
Figure eleven shows a close-up of the reeds in the third octave of the instrument. Here, by looking at the top reed, you can see the three pickups plainly and their relationship to each other and to the reed with which they are associated. Notice that the front edge pickup is a flat, slightly bent piece of sheet metal, whereas the other two pickups are threaded for adjustment. Colored wires attach to terminals held by the pickup holding screws or nuts on each pickup and are the means by which the charging DC voltage is applied to the pickups from the keying networks.
Thus, most of the reeds can generate two or three different waveforms. Different voices or stops in the electrostatic organ result from the use of these waveforms individually or in combinations. The instrument also uses additive synthesis, which I will describe in the Hammond section, to produce the voices of Diapason, Clarinet, and Oboe. The French horn on the solo manual and all of the higher pitched manual flute tones come directly from the pickups over the tips of the reeds. As is typical of a pipe organ, flute pitches are available on the both the upper and lower manual at 16, 8, 4, and 2 foot pitch levels. In addition, there are two mutation pitches, a 2 2/3' and a 1 3/5' pitch on the upper manual, and a 2 2/3 pitch on the lower. These correspond approximately to the third and fifth harmonics of a normal eight foot pitch. Some models also have pitches of 1 1/3 and even 1' on the lower manual.
There is also a soft flute stop, called a Flauto Dolce or perhaps Accompaniment or simply Soft Flute on the lower manual. When this stop alone is on, the keying voltage to the flute pickups on the reeds is considerably reduced in some versions of the electrostatic Wurlitzer, and in others, the keying voltages are applied to the center pickups which give a softer tone than those above the free ends of the reeds.
Besides these, there are also stops labeled Trumpet and Salicional on the upper manual, and Tenor Trumpet and Dulciana on the lower. Most of these are pipe organ stop names. While not sounding really like a trumpet or either a Salicional or a Dulciana, these four stops take their tone from the pickups which are affected by the front edges of each reed. As with the Flauto Dolce, the Salicional and Dulciana stops apply a greatly reduced voltage to the appropriate pickups.
The front edge pickups are, as stated, flat pieces of sheet metal. Since the edges of both the sheet metal pickups and also the fronts of the reeds are very narrow, the resulting electrical waves from these pickups contain sharp spikes, since these edges are in close proximity twice, but only for a very brief portion of the total time of each reed vibration cycle, which results in the production of many harmonics. Figure twelve is a diagram of a triple-pickup reed electrostatic tone generator.
Interestingly enough, because of the physical relationship of the pickups to the motion of the reeds, the signals from the front edge pickups are not in phase with the signals from the pickups over the tops of each reed, but lag them by approximately eighty to ninety degrees. Thus, if you combine the tones from the front edge pickups with those of the pickups over the reeds, some of the harmonics in the resulting mix actually partially cancel out, resulting in a different type of tone, having somewhat the quality of a clarinet with a strong fundamental, lots of upper harmonic development and, with the exception of the fundamental, slightly reduced lower order harmonics.
Another interesting observation concerns minute differences in the sound or timbre of the tone from one note to the next when we examine the tones which come from these front-edge pickups. The tolerances of adjustment on these pickups are very small, with the clearance between the front edge of the reed and the edge of the sheet metal pickup being only around 0.001 inch. Furthermore, exactly where the edge of the pickup is relative to the reed's arc of vibration influences the timing between the two spikes that result as the reed passes the front edge pickups first in one direction and then the other. See this next diagram which shows how this difference can occur.
In normal playing and casual listening, the timbre from one note to the next appears consistent and similar, but careful scrutiny as well as observation of the waveforms on an oscilloscope shows marked differences. A change up or down of as little as a few thousandths of an inch can make the tone sound more like a clarinet, or more like a cello as the timing between the spikes of each cycle of the wave change in time-phase relative to each other.
Interestingly, these minute tonal variations are slightly different from one instrument to another because of minute differences in the adjustments of the pickups. Really careful analysis allows us to develop an audible "fingerprint" of a particular instrument. This, by the way, confirms that the instrument which Ken played on the 67 Melody Lane TV show and on the Columbia LP by the same name is the same instrument. It also shows, however, that the one he played on the Columbia LP "You Can’t be True, Dear," is a different instrument, and likewise the one he used on the radio transcriptions is still another one.
The adjustment of the pickups over the centers and the ends of the reeds is not quite as critical, as the shape of the electrical wave from these pickups is much simpler than that from the front edge pickups. On some of the reeds, the pickups are inserted into slots instead of round holes, so that they can be moved closer to the ends or closer to the centers of the reeds. The motion of the reed strips at the centers is fairly simple, somewhat like, but not exactly the same as the motion of a pendulum. At the tips of the reeds, however, the motion is slightly more complex. The reed strips can flex a little near the free ends, almost like a ballet dancer flexes her wrists when simulating the motion of birds' wings, and therefore, from pickups that are closer to the tips of the reeds we get a strong second harmonic as well as traces of the next several higher harmonics.
At the end of the Wurlitzer section of this article I have provided a set of pictures which illustrates the actual waveforms that are generated by the various pickups on several different reeds and gives you an idea of what the sounds "look like." The pictures are marked according to the note of the scale and also which of the three pickups is producing the waveform. Notice in particular, the differences in the waveforms from the front edge pickups of two adjacent notes, Tenor B (right below Middle C) and Middle C itself. These are from our 4602 console. Actual waveforms observed from Ken's 67 Melody Lane record album appear very similar.
There are numerous advantages to this system over the typical reed organ. As I previously mentioned, the tone of free reeds is not very nice to listen to. Furthermore, it is so distinctive that it is hard to make a reed organ or an accordion sound like anything but exactly that; a reed organ or an accordion. Furthermore, the speech characteristic of free reeds is very slow. Originally, an electrostatic electronic organ using free reeds appeared on the scene in the 1930's. Known as the Orgatron, it had several sets of free reeds with pickups above the reeds. The reeds would remain at rest until keyed pneumatically by electromagnetic pallet valves under each reed. The instrument looked impressive, with a full-size AGO console and various stop tabs above the upper manual, but it was generally not a successful instrument at all.
The lower pitched reeds spoke so slowly that it was virtually impossible to play either fast popular music or any classical music having an intricate pedal figure. To make matters worse, when you let up on a lower pedal note, the reed continued to vibrate or ring mechanically for a disturbingly long time. This of course would generate no more direct acoustical sound, since the operating air was now cut off, but with the charging voltage always on the pickups of these early instruments, it would continue to produce an audio signal at the speakers, thereby making any semblance of pedal definition essentially unattainable.
The soundproofing on the reeds of the early Orgatron instruments was also less than adequate, and a significant portion of the direct sound of each reed would emanate from the console and detract from the sounds from the speakers. In fact, on these early Orgatron instruments, one could play audibly without even turning on the amplification system, in which case the instrument became simply an electrically powered reed organ, and a mighty heavy one at that. It also had the additional joy of a really noisy blower that sounded like a domestic oil-heating boiler on overload. Fortunately, very few of these relics remain in active service anymore, although I have seen a few in funeral parlors. This is probably not a problem, however, as the principal clients of funeral parlors are no longer in a position to hear or care how terrible the instrument is.
The Wurlitzer electrostatic organ of the type we describe here and that which Ken Griffin used was, at the very least, a second-generation descendent of the cumbersome and unmusical Orgatron and had none of its shortcomings. Since the reeds vibrate continuously, there is no lag time. Tones develop when the pickups over the reeds become charged with DC by pressing keys. Letting go of a key switches off the DC, and a discharge resistor bleeds the residual charge off very quickly, so any type of music can be played successfully. Soundproofing is very elaborate, so no reed or blower noise ever intrudes on the music, and the blower itself has an entirely different impeller configuration and is designed to operate very quietly. It is also a much smaller blower than those which we find in the Orgatrons.
In the typical Wurlitzer electrostatic organ, a high voltage direct current (up to 300 volts) goes through a voltage divider to several busbars running the length of each manual and also the pedal key switch assembly. Typically, the keying voltage for normal operation is a +160 volt DC, dropped from +300 by the voltage divider.
Under each key and pedal are several contact wires, which, when a key or pedal is depressed, make contact with these busbars. The busbars are made of insulating material however, but each has a nichrome wire running its length. The nichrome busbar wires connect to the aforementioned voltage divider. The busbars can rotate through about a sixty degree angle. When a stop is off, the appropriate busbar is in such a position that the key contacts touch the insulating material and nothing happens. When a stop is on, however, the busbar rotates so that the nichrome wire is on the top. Then, pushing any key will allow the appropriate contact to touch the nichrome wire on the busbar, completing the circuit and allowing the DC voltage to enter the appropriate keying network for a particular pickup on the reed for the required pitch and tonality.
The keying networks consist of resistors and capacitors.
These are pedal keyers. The manual keyers are smaller, and the various components for each manual keyer are all encased in a housing called a couplate. The purpose of these networks is to "shape" the resulting build up and decay of each keyed tone, so that the tones build almost, but not quite, instantly, and also that each tone may roll-off or decay, again, quickly but not instantly upon key release.
This takes away the inherent "telegraph key" effect which was prevalent in many electronic organs of the period and makes the overall response more like that of a typical theater pipe organ. It also essentially eliminates key clicks. Unlike many other instruments of that period, the Wurlitzer electrostatics sound reasonably acceptable even without any reverberation effect. Figure fifteen is a schematic of an actual keyer for a typical reed pickup and shows the small network of capacitors and resistors that govern the application and removal of the keying voltage from the pickup.
We should now examine another function of a capacitor, and that is its ability to store an electrical charge on its plates. For this purpose, we need to use fixed or constant value capacitors. Typically, these consist of two plates made of metal foil with insulating sheets between, above and below them. To save space, this capacitor "sandwich" consisting of the two foils and the insulating sheets is rolled up into a small cylinder, and the whole is then sealed in plastic or some other protective insulating material. A lead-in wire protrudes from each end of the sealed casing, each wire connected internally to one of the two rolled-up foils. Look again at figure 14 of the keyers, where at the bottom of the picture, you see eighteen black plastic cylinders with colored bands painted on. These are some of the keyer capacitors, in this instance associated with the pedals. The colored bands are a code that identifies the value and value tolerance ratings of these capacitors.
When we apply the DC keying voltage to a reed pickup, a small portion of that voltage causes a tiny, brief current to flow and charge the associated keying capacitor for that particular pickup. As this takes place, the voltage applied to the reed pickup likewise builds up quickly, but not instantly, since the capacitors are charged through resistors. A resistor is simply a device which slows or retards the flow of electric current. In the picture, the tiny cylinders directly above each capacitor are the resistors which serve to slow down or limit this keying current. As a particular keyer capacitor charges, the voltage applied to the associated reed pickup builds up until it is equal to the voltage (+160 volts DC) coming in from the appropriate key contact and busbar. At the same time, the tone gradually builds up in loudness until it reaches its maximum when the keying capacitor is fully charged.
When we release a key or pedal, we remove the source of charging voltage since the key contact is no longer touching the busbar to receive more +160 volt DC. The capacitor now begins to discharge through the resistor, which causes the voltage on the pickup to decrease gradually rather than to drop abruptly. This causes the signal from that particular reed pickup to decay correspondingly. In virtually all real (non-electronic) musical instruments, strings, reeds, struck bars, drumheads or gongs, or vibrating air columns, the stopping of a tone actually takes a slight amount of time as the vibration gradually, but not instantly, decreases. Even though this stopping may take place in only a few milliseconds, it nevertheless is not instantaneous, and it is what we come to expect of every musical sound, be it the horn on a diesel locomotive or a piano string. The Wurlitzer electrostatic organ mimics this important characteristic in the manner that I have just described.
Shortly after the introduction of the electrostatic organs, Wurlitzer developed a percussion sustain accessory, which was available either as an original factory installation or as a later retro-fit for all of the different versions of the Wurlitzer electrostatic organs with continuously running reeds. This device contained extra resistor-capacitor circuitry which could be switched into the keying circuits by multi contact relays to provide percussion sustain. You can hear Ken use this effect in Far Away Places, September Song, and The Nearness of You, among others. In this mode, the appropriate reed pickups would become charged very quickly when you played a key, but this charge would be held by the sustaining capacitors for several seconds after you let go of a key. As the charge was gradually bled off through the associated discharge resistors, the tones would then fade away or ring out gradually.
The beauty of this reed system when used as a variable capacitive tone generator is that the strengths of the generated tones vary with the applied DC voltage. If you insert a means to make the voltage drain off slowly after you let go of a key, the generated tones will then decay gradually, creating sustain.
A second and related effect, which was introduced shortly after the sustain circuitry, consisted of a faster means of applying the voltage to each reed and keyer network. When in this mode, the electrostatic organ tones would begin percussively, somewhat, but not exactly, as those of a Hammond B3 with percussion on and at fast decay. This effect applied only to the flute tone pickups.
Another interesting and musically enhancing effect is that of chorusing or celesting. It is physically impossible to tune these reeds to 100% dead true accuracy. They can be, and indeed they are, tuned very closely and very accurately, but they are all mechanically independent and unsynchronized. Additionally, each reed's electrical output waves contain true harmonics. Therefore, a subtle chorusing or celeste effect develops in the Wurlitzer electrostatic whenever two or more tones get played simultaneously. This occurs not only through the minute tuning imperfections of the reeds, but also because of the difference between the pitches of the tempered notes of the musical scale and the true harmonics of the generated tones.
Whenever the various slight tuning imperfections between the fundamentals and harmonics of the reeds interact with each other, this exactly parallels what happens in real (acoustic) musical instruments, choirs of singers, and orchestras where an infinite and constantly changing array of minute tuning imperfections exist all the time.
At some point during the production of these instruments, Wurlitzer made a major change in the layout of the reed unit and the blower location. The pictures which we show here are from the newer version. In the older version, the reed pans were stacked in two tiers, one over the other, and the blower was on the back of the reed unit. Since the whole assembly had to fit in the console, the blower was placed with its shaft at right angles to the keyboards, which meant that the blower motor had to drive the blower impeller by means of a right-angle gear assembly. This was an extra complication and also a source of mechanical noise.
By 1956, the reed unit had been redesigned to the configuration which we show in these pictures, with all the reed pans on the same level, and the blower assembly on the top. The blower is in line with the motor, which eliminates the need of a right-angle gear unit and its resulting noise and also its requirement for periodic lubrication, which, because of its location in the early version necessitated removal of the reed unit from the console. In the newer version, motor and blower oiling holes are easily accessible with removal of the console back, and the front soundproofing panel of the reed unit housing.
If you look at some of the pictures of the reeds, you will notice that all of the reeds are wired together. This provides a common signal output. Even though the reeds produce many different frequencies and up to three different waveforms, these may all be combined and still retain their individual identities. If this seems hard to believe at first, think of your stereo or hi-fi sound system. All of the sounds of a complete symphony orchestra combine over just two wires from your amplifier outputs to your speakers. Thus, all these different frequencies and waveforms can combine into a single, complex alternating current audio signal and yet we can still pick out individual instruments, singers, etc. when we listen to the sounds from the speakers of our stereos.
Therefore, it comes as no surprise that Wurlitzer could combine the outputs of all of the reeds. In actuality, the first 24 bass reeds are commoned as one group and their signals go to one input on the amplifier designated as the bass channel. The remaining reeds are combined in a different group and their signals go through a separate input stage with much better treble response and also high-pass filtering to suppress low-frequency keying transients which result from the keying networks when in the fast percussion mode and which would otherwise give audible thumps and thuds in the music. These thumps are not a problem in the bass tones, however, since the bass tones are themselves low frequencies, and the percussion fast attack effect is not available on the bass pedal tones anyhow.
The voltages in most electrostatic transducer systems such as the Wurlitzer reed unit are relatively high, and the resistances are also extremely high, resulting in extremely minute audio signal current flows, down in the micro amp range. Because of this, in damp weather, enough of the high voltage DC from the keying circuits can leak through the surrounding air to leave a slight charge on the reed pickups. This results in the continuous production of all of the tones of the instrument. In order to reduce or eliminate this problem, a slight positive bias voltage can be applied to the reeds. A variable resistor in the console controls this bias voltage and is adjustable by turning the slotted movable contact or so-called "wiper" of this variable resistor.
When the bias on the reeds equals the leak voltage on the pickups, there is no longer any net voltage difference between idle pickups and the reeds. Subsequently, the spurious background tones disappear. Because there is DC present on the reeds, it is necessary to confine this DC to the reeds and allow only the alternating current audio signals to proceed from the reeds to the input of the organ amplifier. Although this bias is adjustable, and may at times be tweaked very low, there is also an essentially constant DC voltage on the grids of the preamplifier input tubes. Electrical separation of these DC voltages is accomplished by inserting a blocking capacitor in the signal path.
The actual audio signal of all the reeds in either the bass or treble group develops across a very high value resistive load. Remember when I said we needed to insert a load resistor in the circuit in order to get a usable AC audio signal from a vibrating capacitor? In these instruments, there are two resistors in series with the shallots of all the reeds of a group and ground. Their values are 9,100,000 and 3,900 ohms. [The bias voltage is applied at the point between the two.] At the top end of the 9,100,000 ohm resistor, there is a blocking capacitor, the other end of which goes through a 1,000,000 ohm load resistor, from which the signal develops and then passes to the grid of the first or preamplifying tube in the amplifier section of the instrument.
Recall earlier that we said an alternating current can effectively appear to flow through a capacitor. Direct current, however, only flows in briefly until the capacitor is charged, at which point no more direct current can flow. For the purposes of an amplifier input such as the input stages of the Wurlitzer amplifier, we can therefore think and say that the input capacitor allows the AC audio signal to flow through itself. The end result of this is simply that the signal, which is AC, gets by the blocking capacitor and appears on the grid of the input tube, whereas the DC from the bias and any stray leakage cannot get through.
This, then is yet another function of a capacitor in an amplifier; to allow the AC signal to affect subsequent parts of the amplification circuitry, but to keep any DC from getting through. In this function, a capacitor may be called either a coupling or a blocking capacitor. In subsequent sections of the Wurlitzer amplifier, and indeed in all amplifiers, numerous internal capacitors allow AC signals to flow but block DC operating or bias voltages.
There is still another very important function in these amplifiers which is also a capacitor-based function, and that is power filtering. Since the power that we all use is alternating current, typically at 60 cycles in the USA and 50 cycles in Europe, we have to convert it to DC before we can use it for our amplifiers, musical instruments, and these days, for computers and other digital devices. This conversion is accomplished by a device called a rectifier, which, for our purposes, we can simply say turns every negative half of the input AC into a positive pulse and sends it along with the positive halves to the next part of the amplifier.
This seems simple enough, but if we consider ordinary 60 cycle AC, we need to realize that each cycle consists of a positive pulse followed by a negative pulse of power. These two pulses constitute a cycle. With a frequency of 60 cycles per second, this gives us 120 power pulses per second. One hundred-twenty cycles per second is a little bit lower than the note B right below Tenor C on the keyboard. If we ran this into our Wurlitzer electrostatic organ, we'd hear an overwhelming buzz that would obliterate any and all possible musical signals.
Therefore, we must filter the rectified but pulsating direct current that the rectifier circuit gives us. This we can accomplish by placing several large capacitors in the circuit just after the rectifier. As the voltage of each power pulse builds, it charges these capacitors. When it decreases and momentarily drops to zero between pulses, the capacitors give back stored power from the previous pulse to the subsequent circuitry. To make the filtering really effective, several capacitors follow each other, with either low value resistors or coils of wire called filter chokes between them.
At the input of such a filtering network we have a 120 cycle pulsating direct current. At the output, we have a steady, non-pulsating smooth DC which we can use for powering all of the subsequent electronic circuits, for charging the pickups on the reeds, and for anything else that is needed in the tone producing or amplification portions of the instrument. The main organ transformer, the rectifier, and the subsequent filtering capacitors constitute the power supply of the organ. In the electrostatic Wurlitzer, this power supply is incorporated into the main amplifier chassis that you see in the picture of the general console layout.
A second really important part of this amplifier chassis is the vibrato system. Because the reeds are essentially constant frequency devices, there is no practical way to introduce a pitch-varying vibrato directly at the reeds. Cyclically varying the operating air pressure to free reeds primarily changes their loudness or vibration amplitude, but produces an almost negligible pitch change. Yet, the Wurlitzer electrostatic organs do indeed produce a true frequency-modulating vibrato in a rather ingenious manner.
In the amplifier, all frequencies except for the lowest twenty four can go through a special circuit which by means of a vacuum tube and a pair of resistor-capacitor networks splits the signal into two signals which are always ninety degrees out of phase with each other. Refer to the preliminary discussion on phase.
Associated with this network are two variable gain gating circuits which work in opposition and whose gain is cycled at the vibrato rate. Thus, the instantaneous signal constantly changes phase by ninety degrees, retarding in phase and then smoothly advancing. A change in phase produces a change in frequency as I mentioned in the preliminary section. Therefore, by continually making first one and then the other gating circuit conduct and having one gradually conduct less while the other conducts more, the circuit constantly and smoothly advances and retards the phase by ninety degrees of all electrical signals that are fed into it, in this case, the signals from all of the reeds from #25 to # 85. Thus results in a true frequency modulation or vibrato in the signal.
The Wurlitzer electrostatic organ vibrato, however, was not as full and rich sounding as that of the Hammond, and thus Ken also used a Leslie speaker to add its characteristic acoustic vibrato-tremolo to the instrument's tones. This you can hear in many of the selections on his record, 67 Melody Lane.
On his recordings, Ken did not use the full potential of the electrostatic organ's available percussion effects. I believe that this was not due to any lack of musicianship on Ken's part, because in many of his recordings he demonstrates a great deal of creative ability, but rather upon the limitations of the recording equipment as it existed when he made most of his recordings. The electrostatic organ tended to introduce a very low frequency thud into the attacks of its tones when in the percussion fast-attack mode. While these thuds would be low enough in pitch not to intrude on the music, they might present very real and high amplitude excursions into the audio voltage, and the resulting keying transients on an LP record could very likely cause the groove deviations to be large enough to cause cross-overs between adjacent grooves. Of course, it could also have been just that the percussive fast-attack circuitry had not yet been made available when Ken made his recordings.
Low CCC pedal Middle C Clarinet
Middle C front end pickup Middle C Oboe
Tenorb center pickup Tenoeb front edge pickup
Tenoeb front edge pickup