Philip I. Nelson

Here are some secrets to creating unusual sound effects with the Commodore 128 s built-in synthesizer chip. Using the accompanying program, you can experiment with different sounds without programming. 

Each of the computer s three voices normally plays independently. That is, each voice sounds the same, no matter what the other two are doing. If you make voice 1 beep and voice 2 growl, voice 1 always makes the same beep even if you change voice 2 s growl to a screech. For a simple analogy, 

Ring modulation and synchronization go beyond this to create interactive effects, in which a parameter controlling one voice also affects the sound produced by a second voice. In both cases, the special effect is created by a difference in the frequencies (pitches) of the two voices. 

Synchronization is the simpler of the two effects. You could imagine it as mixing two voices in one channel so that their waveforms intermingle. The result is often a rhythmic or beating effect, produced as the peaks and valleys of the two waves move in and out of step with each other. 

If you program both voices so that their frequencies are always identical, synchronization produces no audible effect. 

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