our ears can distinguish a440 on various instruments by their unique timbre. there are several qualities or characteristics that determine the timbre of an instrument or human voice. they can be altered electronically by a circuit called a "timbre gate." fun experimenting. i have often suggested that pg music add a timbre gate plugin for us to experiment with. nothing so far. peter?

http://en.wikipedia.org/wiki/Timbre

(ADSR—attack, decay, sustain, release) can all be manipulated electronically.

to quote dr gannon: "have fun, eh?"