I'm no expert at all in this regard, but if I had to guess, and you were say, using an iso+mp3, surely it just depends on what mp3's are named to whatever look up song you want to be played whereever? I'm probably thinking way to vague here. So apologies if this isn't the answer you're looking for.
The past tracks for Sonic CD are played via a series of multiple PCM samples, each PCM sample in a bank being the sound of one note to a specific instrument, drum sound or voice. These samples are played by SMPS code for an SMPS engine, however this SMPS varient is altered and designed for PCM playback of 8 PCM channels (I think it's 8, don't quote me on that). The following banks on the disc hold; The SMPS engine (machine code), the SMPS data for the track itself, the PCM samples (including SFX samples). SNCBNK1B.BIN SNCBNK3B.BIN SNCBNK4B.BIN SNCBNK5B.BIN SNCBNK6B.BIN SNCBNK7B.BIN SNCBNK8B.BIN I tried editing one myself once, it didn't sound great, but it was fun to play around with, I'll dig up a download link in 10 minutes. Edit: here we are Stardust Speedway Past. Terrible, but cool stuffs =P
You know, I've been considering to make a modified version of xm2smps which can target the 8 PCM channels of the Sega CD, with the additional feature that the samples in the XM files can be converted as well (within certain limitations of course). However, I'd need more documentation to do such a thing, as I know barely anything about the Sega CD smps.
Yeah, Stardust Speedway Past is the exact track I wanted to edit too. Ha. Well, very informative. Thank you very much. Edit: I actually enjoyed the Stardust Speedway P remix you posted more than the original. lolol
Technically speaking, editing this music is pretty easy. Managing/editing the samples is trivial and the music just uses a modified version of SMPS. I imagine the reason why nobody has done it is either a lack of location data or just a lack of practical knowledge on the subject, much like editing Sonic 2 special stages in the ROM. It's relatively simple, though.
I have a 50%-75% complete disassembly of the engine code I can put up when I finish it (along with sample rips), which leads me to the question: what's the easiest way to make simple patches to the code (like nop-ping out instructions or replacing them with jmp or rts instructions) to test stuff — patch codes in Gens/GS? Actually modifying the ISO file? Mounting the ISO and modifying the files from there? For those of you who want to get a head start, conditions $F4==$F6 (jump) and due to the rather limited nature of the PCM chip's frequency system (which I still don't get 100%) expect to see crazy note offsets to keep the input data looking more like the original song and less like a MOD file with its limited octave range.
What, seriously? I went in expecting white noise, but it came out pretty great. Your modesty irritates me.
