[erikschoster]

> oddly not so much free software

The Analysis & Resynthesis Sound Spectrograph is the closest thing I can think of: http://arss.sourceforge.net It hasn't been updated in a long time but it's still very useful!

Michael Klingbeil's SPEAR is also open source, but a slightly different beast - focused on manipulation of analysis data as a set of partials - it's still insanely useful: http://www.klingbeil.com/spear/

Chris Penrose's excellent Hyperupic was the first tool of this kind I remember encountering, inspired by Xenakis' UPIC system: http://music.columbia.edu/cmc/MusicAndComputers/chapter5/05_... It died with OS9 to the best of my knowledge.

EDIT: Just to say that Alexander Zolotov's work is blowing me away. I didn't realize he was behind SunVox until now, but the portfolio of his projects in this thread is really inspiring.