On Sat, Jun 14, 2003 at 12:12:37AM -0300, Juan Linietsky wrote: To me, an excitation signal is like a pulse, or a step function, which you can use as an input to your system. What comes from the output, you can then use to derive the transfer function of your system, which completely determines the sound of it. Eg. if you manage to record how a cavity reacts to a pulse, you can simulate that environment for other sounds too. This more or less assumes linear characteristics though. Non linear systems are more difficult to identify (to create a model of), and unfortunately most interesting things happen when non linearities are involved (tube amps, analog Moog synths). hope that more or less clears some things up v