Phase mod with PWM

[Grant Richter]

> 
> But, I still get a perception of PM from the triangle as well. So I
> suppose my question would be 'why am I getting PM from a triangle
> wave-pulse output?' However, I may be wrong, perhaps a perfect triangle
> is needed to eliminate hearable PM, and I just didn't have one of those.
> 
I seem to recall the pitch modulation effect of a fixed frequency source
with pulse width modulation is a classic demonstration of the
subjective nature of pitch from some psychoacoustics text?