FL Studio Mobile - Create & save multi-track music projects on a smartphone
Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
Splice Beat Maker - Make and share beats in your browser
ReSlice - Slice your audio with an advanced, rhythmic arpeggiator and FX.
Type Drummer - Drum by typing
zMors Modular - Full featured modular synthesizer for iOS