Unsourced attributions should not be added here. The information below is based on "word of God" from Bobby Prince or other reliable sources.
- The inspiration behind E1M1 - At Doom's Gate has historically been a long-standing issue of discussion and contention among Doom's fanbase. Tracks by bands such as Metallica or Pantera have been suggested as sources, but there is no conclusive evidence that supports any particular track. The track itself is based around a generic heavy metal riff, meaning that it sounds similar to many different heavy metal songs. In a 2017 interview, Bobby Prince clarified that it was not inspired by any particular song, and was written before having listened to any heavy metal music.
- Uses all the same instrument tracks as un19.mid from the unused songs released by John Romero. The main riff of this song is a slight rearrangement of the unused one, the tempo is augmented slightly and all the singular drum tracks are merged into one, but the song structure, MIDI instrument selection and drums are otherwise kept completely unchanged.
- The inspirations for the tracks noted above are substantiated by metadata comments found in the unreleased MIDI tracks (archived 🏛) released by John Romero, many of which are alternate versions of the MIDI tracks used in Doom. See the article: Musical inspirations behind Doom's music.
- The metadata for an early unused version of Donna to the Rescue references Soundgarden - Outshined as its base, but two other unused MIDIs reference the same song as well, yet sound completely different. The metadata may be a leftover note from a different unused MIDI (un32) that is more clearly based on the track.
- The Doom IWAD file includes two title screen MUS lumps, D_INTRO and D_INTROA. The latter is used when using OPL MIDI playback (ie. on an Adlib or Soundblaster card).
"Hiding the Secrets", which is present twice in the IWAD, exists in two slightly different versions:
"Demons on the Prey", which is present thrice in the IWAD, exists in two slightly different versions:
|D_E1M7 and D_E2M5||8591||46d83cbc|
"Intermission from Doom", which is present twice in the IWAD, exists in two slightly different versions:
"Waltz of the Demons", which is present twice in the IWAD, exists in two slightly different versions:
- The D_E1M7 and D_E2M5 version of "Demons on the Prey" has a cymbal instruction in bar 7 that has a wrong Legato instruction that causes the note to play at the very start of the song in some MIDI players. This is never heard in-game, and the D_E3M5 version of the song doesn't have this issue.
- The D_E1M9 version of "Hiding the Secrets" has a broken silence in Track 10 (percussion) that causes the drums to come in at the very first bar, and play 1 bar early for the rest of the song in some MIDI players. This never happens in-game, and the song plays normally regardless. D_E3M9 does not have this issue, and will play correctly in any instance.
- "Waltz of the Demons" is the only one with an audible difference in-game: the bass string instrument that comes in at about 10 seconds in is quieter in D_E2M7 than in D_E3M7. (MIDI channel volumes of 80 and 100, respectively.) The other songs have slightly different MIDI data between versions, but nothing that causes a difference in the way they are played.