Helio Workstation - Cross-platform lightweight speed-painting tool for creating music.
Captain Chords - Write chord progressions in your favorite DAW
Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
RapidComposer - MusicDevelopments RapidComposer: Music Prototyping and Automated Composition Software
Guitar Pro 7 - Create, play and share your tabs
Cthulhu - VST MIDI-FX plugin for harmonic inspiration