Whoops!

Erik Spjut has kindly reminded me that there have, in fact, been several
PWM instruments posted to this list: his own, Josep M Comajuncosas', and
Luis Jure's. I spent some time today playing with all three. They all
have strong points and weak points. I'm still mulling over the best way
to do it, and I think I've got an inkling, but I haven't had a chance to
implement it yet. Stay tuned...