The music in The Binding of Isaac: Rebirth, Afterbirth, Afterbirth †, and Repentance was created by Ridiculon. These soundtracks can be purchased on Steam and on Ridiculon's Bandcamp page, containing 32, 9, 4, and 20 tracks, respectively. Not all tracks heard in-game are included in the OST releases, and some tracks in the OST do not appear in-game or go unused.
Most main floor tracks have a heavier variant that plays when enough enemies or bosses are in the room. In the OST, these variants are generally heard in each song’s second half. What instrument is added is listed next to each track's name in square brackets.
Besides the music listed here, Ridiculon have released three unofficial albums with music relating to The Binding of Isaac, which can be found on their Bandcamp page.
The Legend of Bum-Bo, a Binding of Isaac spinoff, has a title theme that sounds similar to and shares a name with Rebirth’s title theme.
In a Steam interview, Ridiculon producer Jon Evans talked about the OST songs he is most proud of: “‘Sodden Hollow’ for its dripping groove. ‘Sheol’ for even being allowed to be so terrifying in a game OST. ‘Delirium’ for its dank heaviness.” He also points out that “every track we’ve written for Repentance is our fave.”
???'s and Home's music both have “heavy” layers that normally cannot be heard in-game since their respective floors do not contain enemies.
???'s theme can now be heard in-game by various methods, e.g. using Red Key in ???.