Playback of at least 3 music files at one in python
I finally got an answer/workaround.
I am using pythons multiprocessing class/functionality to run multiple pygame instances.
So i can play more than one music file at a time with fully control over playmode and playback position.
I am searching for a way/framework to play at least 3 music files at one in a python application. It should run at least under ubuntu and mac as well as on the raspberry pi.
I need per channel/music file/"deck" that is played:

Control of the Volume of the Playback
Control of the start position of the playback
Play and Pause/Resume functionality
Should support mp3 (Not a must but would be great!)
Great would be built in repeat functionality really great would be a fade to the next iteration when the song is over.

If I can also play at least two video files with audio over the same framework, this would be great, but is not a must.
Has anyone an Idea? I already tried pygame but their player can play just one music file at once or has no control over the playback position.
I need that for a theatre where a background sound should be played (and started simultaneosly with the light) and when it is over, a next file fades over. while that is happening there are some effects (e.g. a bell) at a third audio layer.