RapidComposer - MusicDevelopments RapidComposer: Music Prototyping and Automated Composition Software
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Captain Chords - Write chord progressions in your favorite DAW
Navichord - Intuitive chord sequencer and MIDI controller for iOS
Odesi - ODESI is a music sketchpad that exports your projects to Audio and MIDI.
IsoPad - IsoPad lets you use your Windows tablet to play electronic MIDI instruments.