algorithms for working with sound files

FROM : Darin Duphorne
DATE : Fri Jan 11 23:49:50 2002

Can anyone direct me to a source for algorithms (or objective-c methods) useful
for working with sound files?  Visual Basic, Objective-C or anything would
do.  A good introduction to working with sound file formats would be helpful,
  too.  I am trying to take a sound file (mp3, wma or anything really) and
change its pitch and speed during playback.

Thanks