Rincewind, I've spent a bit of time checking out how the tracks are played in Heretic, and isolating some of them or even getting nice fade-outs to silence with lingering reverb on tracks which do have definite conclusions with a short pause may be a problem. There's even a problem with the title track in that it is cut off and a demo recording with a different track is launched before it finishes.
Only a few of the tracks seem to have a bit of silence at the end, but many which are set up to transition back to the beginning nicely would nevertheless probably benefit from being recorded with no additional short loop to add a fade-out manually, as the way they wrap up on their own is better if they're to be appreciated one by one, on their own.
Of course, this also raises the question of what your intention with such recordings might be, because if they were to be used with source ports, recording each track with a looped section from the beginning might allow someone who knows how to do it to create loop points for seamless playback, the way MusicallyInspired does it with his SC-55 recordings. If the tracks are meant to be listened to outside the game, I think it's better to have them end where they conclude if no looping is involved, so without manually added fade-outs.
Generally, for purposes of listening, I think it would have to be decided which tracks should be recorded without any loops
Setting that aside for the time being, I have tried to look a bit further into what the music or sound card which Kevin Schilder, the game's composer, used might have been, and I found something interesting. He wrote that he usually had access to the latest Sound Blaster, which indeed would have been AWE32 at the time of the game's development. In fact, Heretic entered development the same month as that card was released, in March 1994.
The earlier Sound Blaster, 16, is clearly too limited to have been the hardware he worked on. But there's also the add-on Wave Blaster MIDI synthesizer, which I might have dismissed prematurely in the past. It seems that it and its sequel, Wave Blaster II, had both already been out by 1993. Judging by the recordings available at wavetable.nl, the music produced by Wave Blaster II is quite similar, if not identical, to that produced by AWE32, as they seem to have used the same synthesizer engine. However, the first Wave Blaster sounds a bit different and there's a surprising quality to its rendition of the first level track, ‘Dark’, as the strings there sound more like a chorus and it's quite impressive. On the other hand, the second track seems to sound rather obviously wrong, but it can't be discounted that it's a problem caused by using badly prepared files for the recording, as I think certain parts need to be disabled depending on the music device used.
The recordings in question are available here:
https://www.wavetable.nl/heretic/
Sound Blaster AWE32:
https://www.wavetable.nl/files/comparison/games/Heretic/E1M1/Heretic - HE1M1_The Docks [Creative Sound Blaster AWE32].mp3
Wave Blaster:
https://www.wavetable.nl/files/comparison/games/Heretic/E1M1/Heretic - HE1M1_The Docks [Creative Wave Blaster].mp3
Doesn't that sound rather good? A bit too good to be accidental, perhaps?
It's hard to say if this is worth investigating further, or if it's even possible to do so if there's no one available who could check how the Wave Blaster performs in the game, but I thought it was worth bringing it up before starting anything.
Finally, one thing you could profitably do for now, Rincewind, is to see if the crackling I mentioned occurs for your on AWE32 in the game. The best track to look for it seems to be MUS_E1M7, as it happens right away in the available AWE32 and 64 recordings. You can launch the level which uses this track by starting an episode and typing in
engage17 during gameplay.
Here are the recordings with the distortion:
I apologize if I'm making this more complicated than it needs to be, but I wouldn't like to waste your time if the original card synthesizer used to compose the tracks is after all in doubt.