This is copied from "Improvisation LXXIII" on my YouTube channel:
"The flute sound seems simple enough, but it is deceptively elaborate. It consists of a narrow pulse and a square. The pulse width of each wave form is very slightly and slowly modulated. In addition, an LFO slowly modulates between one oscillator and the other. This means there is a subtle chorus effect from the PWM, a changing of timbre as the narrow pulse changes to a square and then back again, a faint beating of oscillators when the two briefly meet in the middle, plus a delayed vibrato which is either maintained by a smooth connected playing technique or retriggered (and thus, delayed) by a broken disconnected playing technique. Its filter, too, is controlled by the modulation wheel. To deepen the richness of the patch's general tone, the identical sound of Layer A is copied to Layer B and the two are panned at the mixer. So much trouble for a simple little flute sound, but it's always worth it. Of course, all these effects are detectible only when a long note is heard, and that's fine, because they're meant to be musical nuances that don't overly attract attention to themselves.
If it isn't obvious, I think the Prophet '08 makes a superb monophonic synthesizer."
I worked very hard at this patch and it shows the time and effort that can go into designing a monophonic sound with the Prophet '08. Every effect is subtle but adds to the character of what - I hope - is a natural sounding result full of acoustic-like nuances.
I haven't seen one aspect of modulation discussed here before and used in this sound, and that is, modulating the oscillator levels using "Oscillator Mix." By slowly rocking back and forth between oscillators, you can create what seems like pulse width modulation, but without the usual chorus effect, except when they briefly pass each other in the middle and beat. I prefer it best when done subtly, but it's quite an effect when pushed to the extremes, such as when one pulse width is set to "48" (square) and the other is set to about "12" (very narrow pulse). And of course, where you set the "Oscillator Mix" parameter determines which oscillator/waveform gets emphasized more than the other.