String Bass Effect and MIDI on a C2

Traditional Hammond organs are really neat instruments, but with today's technology, we can make them even better. At the time when these typical tone wheel instruments were made, electronics used vacuum tube technology; transistors as such hadn't been invented yet and although almost all of today's modern effects could be done by vacuum tube technology, doing much of it that way was not practical. One of the areas in which a traditional Hammond leaves a lot to be desired is with the tone of its bass pedals. If you use the first pedal drawbar, you will get a deep bass tone that is actually quite useful for many musical effects but it starts instantly and as soon as you let go of a pedal, it stops. Most bass sounds a lot better if it does not stop instantly but gradually fades out or "rolls off" even if this fadeout takes place in only 1 or 2 hundred milliseconds. An abrupt cut off to a bass tone just doesn't sound quite "right" although Hammond's artificial reverb went a long way to correct for this defect.

In order to have sustain, it is necessary to do one of two things. Because sustain implies that the tone of any key or pedal must continue even after said key or pedal is released, it is necessary either to latch the key contacts on mechanically, or else to use some type of electronic keying, where each tone is controlled by a keying circuit which is capable of maintaining (and gradually fading) the tone after you have let go of a key. Generally this latter method, that of electronic keying, is the preferred method, and the one which I used for the sustain or string bass on this C2.

If, when playing such a Hammond, you use the second pedal drawbar, you get a bass tone an octave higher than the low bass tone of the first pedal drawbar, but why the folks at Hammond ever chose to make this a somewhat "hornlike" tone is something that I have never figured out. For much of pops playing, this sound is virtually useless. For years, many Hammond players have circumvented this by a slight wiring change which results in an effect known as "poor man's bass" which places the second and fourth harmonics of Hammond's pedal tones on a separate drawbar from the rest of the pedal. Generally this would be done by using the last white drawbar of one of the two groups of drawbars for the lower manual. The regular second pedal drawbar would then carry the rest of the harmonics of the pedal which gave it the characteristic hornlike tone. By separating the second and fourth harmonics, you would get a much better and more useful pedal tone even though it would still not have any roll-off. If a Hammond that was so treated were to be used in a large hall or a skating rink, the room acoustics would provide this all-important characteristic and the effect of doing this poor man's bass hack was very useful. In my former employment as a rink organist, this would be one of the first changes I would make in any rink I might have to play in, inasmuch as the standard Hammond pedal sound from the second pedal drawbar really was a serious weakness in an otherwise pretty nice instrument.

Hammond could have provided a pedal sustain or string bass effect, but it would have meant using either 25 additional vacuum tubes, or if they had used double triodes such as 12AX7s, they would have needed 13, each handling two pedals, and one 12AX7 would handle the top C only, but the other half of that particular 12AX7 could have been used for some other purpose. However, they did not do this. They did provide a pedal sustain on the early M series spinets, but they used an entirely different technology which held each pedal mechanically latched on and then used a single tube that was triggered each time that you played a pedal and when you let go of the pedal, a capacitor in the tube's circuit would gradually discharge, giving the tone a nice fadeout. The effect worked because of the contact latching in the pedal switch, but that in itself was an extra complication. And on an M3, there was only one pedal drawbar anyhow, so you only had one tone, although you could make it louder or softer as you desired.

However, with today's modern solid state circuitry, multiple individual solid-state keyers for each pedal are small, simple, and consume almost no power at all. Vacuum tubes, on the other hand, needed to contain heaters in order for thermionic emission to take place, and electric heating takes power. I have seen many old electronic organs of various makes that did indeed use multitudes of vacuum tubes for both tone generation and even sustain keying, and quite literally in the winter, such instruments would keep a small room warm just from the heat radiated from their dozens of vacuum tubes all going at once. And you'd in some cases be using 500 or 600 watts just to run the console electronics.

Therefore, knowing all this stuff, I decided that the time for doing some serious upgrades to the C2 that we used at many of our former organ club events would be a very worthwhile effort. My plans for the C2 included four major improvements. First, adding the all-important sustain or string bass to the pedals. Second, adding MIDI capability to both manuals and also the pedals, third, adding X66 style percussion to the lower manual, and finally, the fourth improvement would be variable speed vibrato.

With regard to Hammond vibrato, it is without question the best sounding electronic vibrato of any electronic musical instrument. On the V3 setting, the effect is full and rich sounding, and really is in many ways as good as if not even better than Leslie tremolo. However, what was John Hannert thinking at Hammond when he decided that the rate for the vibrato would be approximately 412 vibrato cycles per minute? Actually, for those of you who are interested, the motor pinion has 23 teeth and the scanner gear has 67. This results in the scanner running at 411.94 RPM which we can round off to 412 RPM. This is way too fast. The folks at Hammond realized this when they designed the vibrato for the H 100 series and also the X66, where they opted for a much nicer vibrato rate of 360 per minute. Running a vibrato at 412 per minute is 6.87 per second and borders on the nervous-singer sound which we have all heard. The nervous singer effect really starts when the vibrato rate is 420 per minute or greater. At 420 vibrato cycles per minute, the rate is 7 per second. Generally a vibrato rate of 7 per second or greater is considered too fast. If John Hannert had used a pinion with 20 teeth and a scanner gear with 67, he would have obtained 358.2 RPM instead which is really close to the ideal rate of 360 per minute or 6 per second.

So the fourth part of my plan is to remove the vibrato scanner from its customary place on the tone generator synchronous motor where it is driven through a reduction gear from a small pinion on the synchronous motor shaft, and place it in the console close to its customary position but drive it with a variable speed DC servo motor, which motor is capable of a wide range of speeds but yet will run at a constant speed for whatever RPMs it is set for. In doing this, we should be able to run in a more realistic vibrato range, such as from a low of 340 per minute to 400 per minute. The arrangement of Hammond vibrato is such that each revolution of the rotating element in the scannner produces one cycle of vibrato, therefore changing the scanner RPMs correspondingly changes the vibrato rate. If we slow the scanner RPMs way down to say 40 per minute, we can then produce a nice celeste effect especially if we combine this extremely slow vibrato with the straight tone such as what happens on the three Chorus settings of the vibrato knob.

The vibrato rate change, however, is a relatively easy job. The addition of pedal sustain and especially MIDI are major projects which is why I moved the C2 to my house so I could do these big projects here where it is much more convenient. Since the C2 is actually my instrument, I am paying the costs of all this work and my budget allows only for pedal sustain and MIDI at this time.

Actually, after I had completed the MIDI capabilities, I soon realized that the third part of this project, that of adding X66 style percussion to the lower manual would entail a lot of extra work and, when compared to the percussion effects available through MIDI, would not really be either necessary or worth the effort, so I decided not to bother with that. So there is no extra set of contacts in the lower manual for percussion; just one additional contact set for the MIDI.

Laurens Hammond was, we may infer from some reading about him and the Hammond organ, convinced that he had developed a complete and virtually perfect instrument which needed no additions or improvements. There are many stories that we can find that detail just how adamantly he was opposed to the idea that anybody such as Don Leslie (the Leslie speaker inventor) should have the unmitigated gall to add something to his instruments that would improve them. Thus, adding things to a traditional tone wheel Hammond organ, such as a C2, were absolutely not in his plans, and therefore Hammond organs are very challenging for those of us who want to add modern improvements and capabilities.

Another problem that Hammond's belief that he had created the perfect instrument gives us is a substantial challenge in working on one. The instrument is incredibly well built and engineered but it has this one glaring exception. The instruments were built evidently by starting with the tone generator and then adding everything else, and doing it in such a way that you must often do an incredible amount of extra disassembly, unsoldering cables, and in general a lot of extra work in order to access areas of the instrument which we would need to access if we are going to make some major additions. The Hammond techs will be the first to agree, Hammonds almost never need major repairs, but when and if they do, it is a first class bitch of a job in most cases.

To begin with, the tops of almost all traditional Hammonds are very well glued to the rest of the console. So having the console top always there makes many otherwise moderately difficult tasks really difficult. Another huge problem is that Hammond did not believe in putting his keyboards on hinges. I have worked on many large electropneumatic pipe organ consoles, and generally the stop rail and all of the manuals are on hinges. You can hinge them up one at a time, like pages in a book, until you have access to the keyboard in question.

But in a Hammond, if you need internal access to either the pedal contact assembly or the key switches of a Hammond keyboard, you must unsolder all of the wires that connect these keyboard terminals to the tone generator, after which you must remove the desired assembly from the console. So a five minute key contact repair that necessitates entering a Hammond keyboard or the pedal switch assembly, instead of taking maybe a total of a half hour, will require you to spend probably two days on the project, depending on what is wrong and what needs to be accessed.

Realizing this, one of the very first things I did with this Hammond C2 Console was to break the glue joints holding the top to the rest of the console. And Hammond cabinet makers made really nice glue joints so it becomes an incredibly tricky and difficult task if you wish to remove the top of the console and not do any visible damage to the console woodwork. Fortunately, when this console was built, glues such as Titebond III™ were not yet available. That would have made removing the top without serious woodwork damage almost impossible. But I must add that making the top removable makes a lot of what I did in the manuals so much easier than leaving the top in place, so definitely this was a necessary task, and also a great improvement. When it came time to put the top back, I went to a good hardware outlet and purchased some really nice looking brass screws and brass finishing [cup] washers. These do not look either out of place, and they'll also make it much easier when eventually the wire to the back of one of the drawbars breaks at some point and I will need to resolder it.

The most important of all part of this task was to leave the C2 as a complete Hammond organ. I have read several accounts including advertising by at least one firm that will take a traditional Hammond organ, remove all of the original Hammond mechanism, and then utilize the excellent Hammond key contacts for operating MIDI. So effectively what they do is wind up with a console that looks like a Hammond organ but is actually just a MIDI controller. My opinion of doing this is pretty much the same as it would be if I heard of anybody turning a Stradivarius violin into a ukulele; that such activity is an unforgivable willful destruction of a valuable and good musical instrument with complete disregard for the legacy that you are destroying. There will never be any more tonewheel Hammonds made. The people involved with their design and construction are either dead or long since retired. The Hammond factory buildings still exist, but all of the original machinery used in making tonewheel Hammonds is long-gone and different activities take place there today. Therefore, my decision in upgrading this C2 was first of all to preserve it as a fully functioning Hammond C2, and then see if it would be possible to add MIDI capability and a string bass without stopping it from first of all being a traditional Hammond organ. My one concession to this was the elimination of the horn-like tone of the second pedal drawbar. But this is a very small change, and does not stop the instrument from still being a complete Hammond organ first of all, whatever other changes might be made via augmentation.

A task such as this necessitates fabricating a lot of things specially or otherwise getting into the inner workings of a Hammond organ to a far greater extent than you might think necessary at first in order to get around the restrictions that Laurens Hammond presents to us in these instruments. Since he felt that nothing needed to be added, he did not provide any room or even consideration in the design of his manuals and pedal switching systems that would allow for either easy internal access or for the the installation of additional key contacts. Not that it can't be done. It certain can be done, but not without great difficulty. For an interesting account of a similar project, check out Dan Vigin's installation of MIDI in the upper manual of an X66 HERE.

So here is the story of my modifications to a standard Hammond C2; the addition of pedal sustain bass at three pitch levels, 32' 16, and also 8' with the decay time and the volume fully adjustable to the musician's preference, and also the capability of playing any MIDI devices, such as external keyboards, MIDI sound modules, or even the sound cards in a computer directly from the keys and pedals of this Hammond, It is entirely possible that in the course of doing this work I shall make discoveries or figure out ways to "do it better," and I will thus include such information on these pages as it may become available.