Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
MuseScore.org - Create, play back and print beautiful sheet music with free and easy to use music notation software MuseScore. For Windows, Mac and Linux.
cassini - Polyphonic Synthesizer for iPhone/iPod touch
Guitar Pro 7 - Create, play and share your tabs
zMors Modular - Full featured modular synthesizer for iOS
Finale - Finale, the world standard for music notation software, lets you compose, arrange, notate, and print engraver-quality sheet music.