Music Mixing Software

Hello,

Is there a simple *non-real time* music/audio/mp3 mixing software available for Mac? I want to be able to change the pitch/tempo of the tracks and mix together multiple tracks so as to create non-stop sets.

I used to use Acoustica's MP3 Audio Mixer on the PC but they don't make it for Mac. Anyone know of a similar program for Mac?

Please help!

Thanks.