What is a good cross platform audio processing library?

Question

I'm looking for an audio processing library that i can use to do some on-the-fly audio editing in my program, such as turn a knob and it'll increase the pitch of the audio file being played, without saving the change to the song file itself. And i plan to make this program for windows and mac so i would need a cross platform library. I don't have much money to spare so it can't cost too much either. My program will be commercially available if that changes anything. Thanks in advance for any help.

Answer 1

SoX at http://sox.sourceforge.net/

Wavesurfer at http://www.speech.kth.se/wavesurfer/