Vox is a little and simple music player for Mac OS X with support for many file types, including FLAC, MP3, AAC, Musepack, Monkey's Audio, OGG Vorbis, Apple Lossless, AIFF, WAV, IT, MOD, XM, Games Music and many others. Includes numerous effects like Equalizer, Reverb, Time Stretch, Pitch Shift, Echo. Moreover, all supported files can be exported to AAC+, Apple Lossless, WAV and other formats with enabled effects.
Homepage / Download (10.5+ / 10.4)

One feature that could be really useful for musicians is the ability to slow down tracks using the time stretch feature (similar to Capo and Amazing Slow Downer). Unlike those two apps, Vox is free.