Unused Doom music

In June 2007, John Romero released a collection of unused MIDI music tracks on his website, which were created as part of Doom's development but not used within the game. Some of the tracks were used in the game in a different form. In total 31 .mid files are in the collection, and these are of historical interest, as they give insight into Doom's development process (the tools used by Bobby Prince) and also insight into the musical inspirations behind Doom's music.

Many of the tracks are inspired by tracks by popular heavy metal bands and are annotated with metadata that names the song from which they take inspiration. This provided confirmation to some fans who had long noticed musical similarities between certain tracks in Doom's soundtrack and well-known heavy metal songs.

In a 2017 interview, Bobby Prince clarified that the "un" prefix for the filenames is an abbreviation for "use not", indicating that these files were specifically not intended to be used in the games for legal reasons.