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Programmable Drum Set

It's fascinating, the way the development of some products is a struggle from beginning to end, while others seem to almost design themselves.

This programmable drum unit is an example of the latter. In retrospect, it seems to be an amalgamation of effortless insights and serendipitous "discoveries" that all came together with such perfect timing that the product itself just sort of spontaneously appeared. No Sweat.

And, best of all, now that it's designed I discover new things that it can do every time I play with it.

But, this is getting ahead of myself. First I ought to tell you what it does - and more importantly; why it does it. You're really going to like this one.

As I see it (and I've designed these things before so I certainly have a right to an opinion) past percussion units have had three major failings:

1) They do the same thing again and again.
2) They do the same thing again and again
3) They have no provision for unusual time signatures.

Are you surprised that the first two are the same? I was. I'm talking about two different "sames" though. Let me explain.

The first same is that other than choosing very generalized and idealized "classic" rhythm patterns, you have no control over the percussion score that is generated. Every time you punch up "tango" it's going to be just like the last tango. Programmability is the obvious key here. You can produce as many different tango's as you can dream up.

The second same is that the same pattern repeats, at best, every couple of measures. Real music isn't played like this. In real music you've got intros and bridges and jazzy stuff like that. This unit takes care of that by giving you a BRIDGE key. When this control is activated, instead of repeating the same pattern again, the unit switches to a separate pattern and repeats it as long as the bridge key is activated. When the bridge key is released, the unit shifts back to the first pattern and begins playing it again. I should mention that the shifting from one pattern to another happens automatically only at the repeat points (the end of the pattern - more details on this shortly), but it can be "forced" to happen anytime.

Every rhythm unit plays 2/4 and 4/4 times with no problems. The ones that are worth anything at all also include a couple of 3/4 or 6/8 things too. But, I don't know of a one that has provision for even 5/4 time - and as "unusual" time signatures go, that one's pretty common. This new unit can be programmed for any conceivable pattern, no matter how strange the time signature.

Earlier I said that serendipity was a major contributor to this product and here's what I had in mind. All of the labeled squares that you see on the control surface are non-mechanical touch switches. Even the slightest touch activates them (the touch switches will be analyzed in the next issue, but we're not going to be concerned with the circuitry now, only the operational details of the entire unit). The design of these switches was purest dumb luck.

Let's talk about concept for a moment.

Inside the unit are drum circuits, logic and 256 eight bit words of semiconductor read/write (RAM) memory. Each of these words represents an "event" that was, or will be, programmed. When the unit is playing a pattern back a clock whose speed is adjusted by the TEMPO control causes a counter to step through the events. Whatever is recorded at each event is going to happen. What's recorded can be one of three things; a drum beat, a rest, or an instruction that causes the circuitry to go back to the beginning of the pattern and repeat it.

256 events is a lot of memory for a thing like this. Too much, in fact, if it represented only a single pattern. It doesn't. It represents 4 different patterns, each of which can be up to 64 events long. The 4 different patterns can be further broken down into two 64 event "scores" each of which has an associated 64 event "bridge". The slide switch labeled SCORE 1/2 allows you to select either score for programming or playback.

Let's say that we want to program a pattern:

The first action would be to touch the RESET pad. This resets all of the internal circuitry and will in general be the first step in doing anything.

Select which of the two patterns (SCORE 1/2) you are going to record and set the slide switch accordingly.

Press the PROGRAM push-button and observe that the PROGRAM LED lights indicating that you are in the program mode.

Now the DRUM pads are activated in turn to produce the desired rhythm pattern. And remember that most musically interesting rhythm scores will have as many RESTs as drum sounds. When you reach the point at which you want the pattern to repeat, touch the REPEAT pad.

The setting of the TEMPO control during programming is not critical, but leaving your finger on any DRUM pad will cause that drum sound to repeat at the TEMPO rate. This also causes that drum sound to be recorded in successive events in memory.

Programming a BRIDGE is essentially the same as programming a SCORE, the only difference is that you have to get the unit into the BRIDGE mode (as indicated by the BRIDGE LED) by touching BRIDGE and RESET before pressing the PROGRAM button.

Playing back a score is simply a matter of setting the tempo desired and touching the PLAY pad. When you get ready to play the BRIDGE pattern, touch the BRIDGE pad and at the next REPEAT event the unit will automatically shift to the bridge, play it, and then shift back to the main pattern. If the BRIDGE pad is continuously touched, the bridge will play continually.

All of that would be plenty neat by itself, but there's more...

You don't have to start playing with the main score, you can treat the bridge as an intro by putting the unit into the BRIDGE mode and touching PLAY. When the end of the bridge pattern is reached you will automatically shift to the main score.

You don't have to let any pattern go to completion, touching the REPEAT pad at any time will cause the drum set to go back to the beginning.

If the BRIDGE pad is touched at the same time as REPEAT, you will go to the beginning of the BRIDGE. This opens up enormous possibilities for having programmed rhythm patterns that seem to never repeat.

You don't have to play a score back at a fixed tempo. Touching the REST pad causes the drums to play at the TEMPO setting (without being "locked" into PLAY mode). Tapping the REST pad causes the drums to play at the tempo of the taps. The unit has an external Synch input, so it's tempo can easily be governed by an external clock (a sequencer, for example).

The two programmable scores that you have available don't have to be entirely different, they can be part of the same score and judicious use of the SCORE 1/2 slide switch will allow for switching back and forth between the two parts.

If you're beginning to get the idea that this unit is an extremely versatile device, I think you're right. It's not going to replace a living percussionist (a good one anyway) but it does come a lot closer than anything else that I know of.

The programmable drum unit is battery powered and runs off of 4 "AA" size pencells and a single 9 volt transistor battery. The nine volt battery supplies bias to the noise source in the snare circuit and should have essentially shelf life. The pencells should be good for about 20 hours of intermittent operation.

There is still one switch key that we haven't looked at, the SAVE switch.

The Programmable Drum Set uses 2112 type memories. They're volatile, which means that if you turn off the power to them they forget everything that was programmed into them. The SAVE switch allows you to turn off power to all of the drum circuits, logic, etc., while maintaining a reduced voltage to the memory chips. It allows you to save a pattern without leaving the unit on all the time and draining the batteries. A nice touch.

Previous Article in this issue

Convert Your Pygmy into an Electro-Larynx

Next article in this issue

Fundamental Music Notation

Polyphony - Copyright: Polyphony Publishing Company


Polyphony - Oct 1976

Donated & scanned by: Vesa Lahteenmaki

Feature by John Simonton

Previous article in this issue:

> Convert Your Pygmy into an E...

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> Fundamental Music Notation

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