Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
Guitar Pro 7 - Create, play and share your tabs
music21 - Music21 is a Python-based toolkit for computer-aided musicology.
Synfire - The comprehensive Music Prototyping Studio for professionals and enthusiasts.
Harmony Assistant - Harmony Assistant is an unbeatable software for computer-assisted music composition and editing.
MMA - “MMA—Musical MIDI Accompaniment” is an accompaniment generator.