amp envelope analysis for later synthesis

Hello, all.
I'm working on a piece for percussionist and electronic performer, and am trying to figure out some interesting ways to create sounds. (this is part of an undergraduate research grant)
The idea is for the electronic sounds to be modeled after the live player's acoustic instruments.
Originally, I was recording samples of each of the instruments to be altered in Max and and played back via a MIDI drum pad. This works OK for my purposes, but I was starting to look into actual synthesis as well.
What I would like to do is have Max analyze the sound of each instrument (this can be done ahead of time before the performance) in order to reproduce facsimiles triggered by the electronic performer. I know how to analyze the pitch material, but now I'm looking at getting the amplitude envelope. I've seen patches for envelope following, but how can I have Max listen to a sound once and remember that amplitude envelope for later synthesis? The way I'm designing the piece, it's OK if the data needs to be edited ahead of time.
Thanks.