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.

Sibelius is a scorewriter program, created by Sibelius Software (now part of Avid Technology) for Microsoft Windows, OS X, and historically RISC OS.

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.

Compose or publish music notation, produce teaching materials or learn the language of music — Dorico lets you make beautiful music, fast.

Flat lets you write sheet music with your friends in real time with a nice music notation editor.

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.

Frescobaldi is a LilyPond sheet music text editor. It aims to be powerful, yet lightweight and easy to use. Frescobaldi is Free Software, freely available under the General Public License.

Anvil Studio is a free Windows 7/Vista/XP/2000/98 program designed for people who want to:

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.