Patch Parameters--Booster Use for Making PWM
(XP-80 Owner's Manual, pg. 49. Copyright 1996, Roland Corp.). In the illustration above, Tone 1's waveform (WG1) acts as a LFO (Low-Frequency Oscillator) on Tone 2's waveform (WG2). This is because Tone 1's frequency (pitch) is lower than that of Tone 2's frequency causing the sum of the two waveforms to have a "beat" effect (pulsating volume). When a Booster is applied (especially with gain turned up), the top (and bottom most of the time) of the waveform is "clipped," or cut off, resembling a pulse. As the waveform pulsates, the louder portions get clipped more by the Booster than the quieter portions, thus modulating the width of the clipped waveform simulating PWM (Pulse Width Modulation). The illustration above uses Tone Structure 4 (though Structure 3 can also be used) to create this effect.
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