mod sound file editing library?

[Seth Delackner]

Could someone please suggest a library that will allow me to generate
mod files?  Any mod format will do, or perhaps midi with custom sound
samples replacing specific instruments.

I have found lots of gui editors, but I am writing a song editing
program and it seems a waste to develop yet another song format.

* Instruments have to be samples (thus MOD/XM/...).
* cross platform: at least Win / OS X.
* I'm writing in Python, but I would be happy to find a C/C++ library
  even if I have to write the python wrapper for it.