GNU Denemo is a music notation editor that lets you rapidly enter notation for typesetting via the LilyPond music engraver. You can compose, transcribe, arrange, listen to the music and much more.

EasyABC allows you to edit and play abc files. It supports conversion from MusicXML and MIDI to ABC. The latter uses a custom implementation (midi2abc is not used) in order to produce very readable ABC output. Direct midi input is supported for people with a midi keyboard.

DGuitar is a Guitar Pro (GP4, GP3, GTP) viewer/player that works on Windows, Mac, Linux, BSD, Solaris, and any other operating system that has Java Runtime Environment 1.4 or later installed.

DaCapo Editor is a free Open Source music sheet editor which allows to easily create nice looking partitions. It is available as a web application as well as a desktop application for Windows, MacOS and Linux.

Power Tab Editor is a free tablature authoring tool created by Brad Larsen for Windows. It is used to create guitar, bass and ukulele tablature scores, among many others. The current version uses the *.ptb file format.

MC Musiceditor is free/open source (GPLv2) music notation software (Windows). It has been developed with only one purpose: to make life of musicians easier when making scores. This results in a userfriendly editor which makes professional scores without requiring specific...

ABC, a text based music score manager-editor for free. You can copy, transpose or play these songs, import midi-music files, export to midi, to pdf, to web page or to any other printable format.

Music21 is a Python-based toolkit for computer-aided musicology. Applications of this toolkit include computational musicology, music informations, musical example extraction and generation, music notation editing and scripting, and a wide variety of approaches to composition, bo.

Jazz++ is a MIDI sequencer/composer. Create your own music.

Busker is a complete set of tools to create musical arrangements from sheet music (chords + melody staff). It uses Yamaha compatible styles (thousands can be downloaded for free) for auto-accompaniment.

NoteWorthy Composer is a graphical score editor intended for the creation of sheet music, but it can also import and export MIDI and Karaoke files and can export graphical WMFs. The user interface works either from the keyboard or the mouse.

NtEd is a GTK+ score editor. It intends to be really WYSIWYG: what you see on the screen is exactly what you get on printer output. It supports up to 4 voices per staff, drum notes, 5 lyrics lines, N-Tuplets, context changes, repeats with alternatives, configurable music...