I had the opportunity to compare three similar midi synthesizers: Roland SC-55, Roland SC-55mkII and Roland SC-55ST. I recorded each of them playing the first four tracks of Doom 1, taking care to use the exact same process each time.
This was interesting to me, and I hope others find it of interest too.

The sound code was omitted from the public release of the DOOM source, and its music format, MUS, is slightly different from MIDI, with reports of erroneous MIDI conversions. Therefore, I decided to run the full game on an actual 486 dx2/66 in order to ensure the generated music is true to the original.
In my recording setup, the 486 starts Doom-1, which instructs the SC-55XX to produce the sound. A cable is connected to the SC-55XX output and to the high-end (ish) recording equipment input (ALC S1220A).

The recordings and a description of the recording procedure is available at
https://drive.google.com/drive/folders/1uR0Ft … aHA?usp=sharing, in flac and wav format, including raw recordings.

Findings:
1) All sound marvellous at track E1M1.. E1M3. I have trouble noticing differences, no parts sounded off or missing.
2) Both the SC-55 and SC-55mkII, but not the the SC55ST, had very noticeable uneven stereo in track E1M4. It sounds wrong, the percussion on the one channel is too loud. Here the SC55ST sounded best. The same behavior was seen when recording from the RCA output plugs as the phones jack, as well as with different recording equipment (M-Audio Fast Track Pro). In E1M2 there is very clear separation between the two channels on all three devices. There are multiple possible reasons, but I don't believe it to be a problem particular to my units or recording equipment, given the above. A possibility is that this is how the MIDI music was generated. Another is that this is a shortcoming with SC55 and SC55mkII fixed in the later SC55ST.
3) The waveforms for the noise looks very similar between the three units (cursory visual inspection only)
4) The volume was a bit low on the SC55ST
5) My favorite was the SC55ST

I no longer have the SC55ST, as I was just borrowing it.