Does Audacity do it? Don't know if they do a MAC version but worth a look? Failing that send them over and I'll convert them for you on my PC.
AL
Audacity is a great program and I'm sure it will do the job. There definitely is a Mac version - checkout
http://audacity.sourceforge.net/As mentioned in other threads, I have used it to help in my playing by
- slowing down pieces - without changing the pitch, so that I can play along;
changing the pitch of pieces so that they are in an appropriate key for my box.
I would strongly recommend you to download a copy.
Cheers
Pete