Music For Makers - Licensing good music has never been this easy.
Groovebox: Beat & Synth Studio - Make Music & Play Instruments
TunePocket - Download 11,000+ royalty free music tracks and sound FX. Buy once, use forever. New music added daily. Save over 50% compared to most popular similar services. Incredible value!
Scratch Track - Scratch Track is a simple and powerful application that offers services as a recording app to capture song ideas.
Incompetech - Royalty Free and Creative Commons Music Archive
BeatStyle - A mobile recording studio!