Contains an "Anthem Composer" which allows you to write simple tracks. Limited and gimmicky, but a fun mechanic to mess around with.

Features a lute which can either be played or used as a weapon. Playing manually is seems near impossible, so most bards play using external programs to load MIDI files.

Features a functional sequencer called the ByteBeat, which is somewhat limited but can be used to make some pretty cool tracks.

Includes a few instruments which can be used to play predetermined tracks. Pretty limited, but it technically counts.

Features a Shakuhachi you can play, albeit not manually. Can be used to control the weather. Iki Island has a minigame where you control it directly for a few songs.

Features a few different instruments which are completely functional, as far as I can tell. Pretty cool but requires you to play Rust, which I do not.

Features a Trombone playable with the mouse. Has a selection of included tracks, and possibly a future level editor. Sounds terrible, but that's the point.

Includes a limited sequencer which can be used to write short loops, and a playable stringed instrument with a Guitar Hero-esque interface which can play custom songs.

Has a few playable instruments, and collectible music sheets which show you how to play certain songs.