Spotify - Map shows when two people play same song at same time
Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
SOUNDS - Discover music with friends
nlog Synth - Professional Virtual Analogue Synthesizer ::: check nlogmusic at YouTube :::
Songlink - Share music with anyone.
cassini - Polyphonic Synthesizer for iPhone/iPod touch