MuseScore is a free music notation and composition software available for Windows, Mac, and Linux.

A Multitrack tablature editor and player.

The software to compose music, transcribe your favorite songs, or simply read the thousands of tabs available on the Internet.

Rosegarden is a well-rounded audio and MIDI sequencer, score editor, and general-purpose music composition and editing environment.

Impro-Visor (short for “Improvisation Advisor”) is a music notation program designed to help jazz musicians compose and hear solos similar to ones that might be improvised. The objective is to improve understanding of solo construction and tune chord changes.

Band-in-a-Box is an intelligent automatic accompaniment program. You can hear and play along to many song ideas and go from "nothing" to "something" in a very short period of time with Band-in-a-Box as your "on demand" backup band.

GNU LilyPond is a computer program for music engraving. One of LilyPonds major goals is to produce scores that are engraved with traditional layout rules, reflecting the era when scores were engraved by hand.

Aria Maestosa is an open-source (GPL) midi tracker/editor. It lets you compose, edit and play midi files with a few clicks in a user-friendly interface offering keyboard, guitar, drum and controller views.

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.

SongStuff is a software solution for song creating and recording. There are also a music notation module and a beat library in the program. This application is a very useful tool for song writers and music makers.

alphaTab is a cross platform music notation and guitar tablature rendering library. You can use alphaTab within your own website or application to load music sheets from files like Guitar Pro or use the built in markup named alphaTex.