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.
Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
music21 - Music21 is a Python-based toolkit for computer-aided musicology.
MuseScore - Our goal is to let musicians from all over the world create and share their works, as well as to make learning music exciting, easy and available for all.
Harmony Assistant - Harmony Assistant is an unbeatable software for computer-assisted music composition and editing.
Guitar Pro 7 - Create, play and share your tabs