[plt-scheme] audio processing and music generation

Is anyone doing audio processing and/or music generation with PLT Scheme
recently?

A non-programmer wants to implement a couple ideas that involve DSP to
extract features of music audio signals, and (separately) generation of
music and non-music audio.

She's willing to learn a little programming (in Java or perhaps Scheme),
but she'll need pre-written reliable libraries for audio/music.

The required libraries can be particular to Mac OS X or GNU/Linux, but
ideally her programs would work on both platforms.

Ideas?  Or, if there are portable C libraries you'd recommend strongly,
I might be able to write the PLT bindings myself.