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A column devoted to answering your questions about PAIA , electronic music or any other area which might be of interest to our readers.


I would like to know how to make the sound of the falling rain and the sound of thunder.
Dale Naylor

Dear Dale,
The quality of sound is very subjective; everyone thinks of something different. Most thunder and rain sounds are based on noise in one way or another. For rain, try putting noise through a low pass filter. This produces a constant (steady rain) sound because the volume is not changed significantly. Thunder is a little more complicated because of dynamics changes. You'll want to construct a Percussion type sound so begin with the Function generator and a VGA, and because higher frequency sound travels faster than lower frequency sound some sort of filtering will be helpful.

We hope that this aims you in the right direction. As always, experiment with different combinations, until you have something that sounds most like thunder and rain to you.


I have a Sony 630 deck, which is a nice machine, but, my tastes are grandiose. A lot of my favorite classics involve from 8 to 16 voices. I'm sure that there are some more inventive individuals than I who, working within the limitations of a home stereo system, have designed and built supplementary equipment to expand on their own capabilities. Has anyone come up with a modification or technique to get 16 clean and separate voices together using a three-head stereo deck?
Mark Meyering

Dear Mark,
Tape recorders and their use and modification is an important part of synthesis. You'll be seeing more on this subject in future issues of Polyphony. Meanwhile, some helpful information is contained in the "Handbook of Multi-Channel Recording" by F. Alton Everest, available from TAB books, (#781 - $10.95, hard cover) (Contact Details).


Is there any way that I can convert my 2720-5 Control Oscillator to provide a pulse wave output?
John Finney

Dear John,
Until a 4700 series Control Oscillator is released, the easiest way to obtain a 5 volt pulse wave is to run the variable output of your -5 into the trigger input of the 2720-4 Function Generator. Set the Function Generator attack and decay controls at minimum, and switch the expand control to off.

As the output level of the control oscillator is increased, the Function Generator will start to fire and produce narrow pulses. As the Control Oscillator output is increased further, the width of the pulses will increase to a maximum of around 60% duty cycle due to a continually larger portion of the '-5 output being above the trigger level of the function generator.

If the envelope generator is already being used in the patch, an a alternative is to feed the control oscillator variable output into the Envelope Follower input. The step output of the Envelope Follower wall then be the source of a 5 volt pulse wave.

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Polyphony - Copyright: Polyphony Publishing Company


Polyphony - Feb 1976

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