Hey guys. I am working on a game right now (using SFML) with levels being generated "infinitely". Anyway, I wanted to have a simple looping melody for "music" and I was going to shift the tempo up each level. As far as I know, OpenAL and SFML can't do this - it is quite a difficult operation (if it can even be done realtime on my hardware, while there is other stuff using my CPU). So I am looking for a different audio library to use. Either one that can change tempo of an mp3/ogg/whatever without shifting the pitch too, or perhaps a library to play MIDI or popular tracker formats, or even a SID emulator or SPC700. Has anyone here got any experience with anything like this or any suggestions? By the way, I have thought about having a different loop for each level, but when 15+ levels is a reasonable amount to get through on your first play, this seems a little excessive. Cheers

Cheers, that one's on my list to try, although it's OpenAL based, but I still don't know if OpenAL can do what I want, or if it can't, whether or not this feature can be implemented in software and then use OpenAL, I'm not really sure.

Currently checking out fmod, although I dislike the licensing.

I have not tried it yet, but I recently stumbled over SoundTouch, which might be interesting for you:
http://www.surina.net/soundtouch/