I'm running into a strange bug (at least it seems like a bug to me) in the Mac version (3.0.2.98) of Prophet V3.
In Prophet 5 mod, bring up a patch called Pro Clarinet.
In the Mixer section, turn Osc A all the way down. You will hear Osc B with pulse waveform, but during the Attack, it sounds like the pulse width is being modulated by something (envelope with a quick attack). If you turn Osc B PW knob all the way to the right, it is especially pronounced.
However I can't see anything that might be modulating it... in the P5 it is not possible to have an envelope modify Osc B PW. Even when I switch to P5/VS hybrid mode, the mod matrix doesn't have any modulation routings. So I have to assume this is some kind of bug...even though in the case of the clarinet sound, it is probably intentional because it adds a cool clarinet attack element.
The only reason I noticed this is because I was using this patch as a starting point for a custom patch I was working on, and no matter what I tried, I could not turn that PWM off.