Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
ChordU - Extracts chords from any song, integrated YouTube.
ReSlice - Slice your audio with an advanced, rhythmic arpeggiator and FX.
Guitaa.com - Turn ANY song into chords, play along with interactive chords and diagram, transpose, loop, tempo control.
zMors Modular - Full featured modular synthesizer for iOS
Chordify - Chordify turns any music or song (YouTube, Deezer, SoundCloud, MP3) into chords.