NtEd - Music Score Notation editor.
Aberoth - Aberoth is an Action-Adventure, MMORPG and Fantasy-based video game by Jarbit.
music21 - Music21 is a Python-based toolkit for computer-aided musicology.
Browserquest - Browserquest is a MMORPG (Massively Multiplayer Online Role-playing Game) video game developed and published by Mozilla Foundation.
Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
RPG MO - RPG MO is a Free-to-play, Action-Adventure, Massively Multiplayer Online, Browser-based, Fantasy and Role-playing video game developed and published by Marxnet.