I'd like to announce that I'm now accepting beta testers for my Free Software musical concatenative synthesis system, called SchemeMosaic. It uses a nice Emacs front end to control a Scheme based DSP (Digital Signal Processing) system called Snd (created by Bill Schottstaedt.)
As it is extensible, it may be of particular interest to those interested in using Emacs to help with audio processing tasks. Plenty of screenshots, videos, and audio samples are available on the website at
http://xelf.me/scheme-mosaic.html
I have recently formed EMSIG, the semi-informal Emacs Multimedia Special Interest Group, we hang out on Freenode's channel #emsig and it would be so nice if you visited us to discuss ideas.
SchemeMosaic uses Cell-mode, a nice spreadsheet GUI control for Emacs. I hope you enjoy! Please let me know if you are interested in trying it out.