It's amazing what you forget after 20 years, isn't it?
It's also amazing how, in an instant, everything suddenly comes back to you. And when it does, it brings with it the realisation of how *bastard hard* everything is going to be!
Anyway, several hours later (having lost an argument with Linel's Sound FX: yeah OK, you're right, you *don't* load "datas" (which I have) but only "songs" and "instruments" (which I don't) so let me find and install a module ripper I've just remembered that saves both out, only to later discover a newer version of Sound FX that *does* load "datas" when it's too late) I now have my original YM/AY-emulating track loaded in with its clever, 4-mat style 64-byte looped square waves and white noise instruments.
I'd forgotten that, in order to make the arpeggio/vibrato/portamento effects sound authentic, I'd sequenced the track in double-time, so every pattern scrolls down the screen at break-neck speed. I also quickly realised I've forgotten everything else. This is definitely the best starting point though, so I'll step through it bit by bit, trying to remember how I put it together when I get more time - hopefully tommorow.
I intend recording the YM and AY originals and separating out the channels somehow (I haven't looked yet, but I'm guessing any decent YM/AY player or plugin will allow me to do this, otherwise I'll run them through emulators that *surely* have that option.) I will then remake it bar by bar in SoundFX.
EDIT: Oh. I've just remembered that, in a past life when I knew how to do such things, I had to hack the SoundFX playroutine to convert it from CIA/interrupt driven to, er, cycle-based(?) (i.e. so you could call it from a main-loop) and I've no idea if anyone else ever did the same and that the source is out there somewhere... This was the routine used for both the Magnetic Fields' Spaced Out disks featuring my stuff (which made my CIA-timing dependent tracks sound horrible). Can't remember if Spook enhanced it.. Not going to work.
EDIT: I've just remembered you can load SoundFX datas into MED and save them out as MODs... doubt my clever 64-byte looped waveforms will be respected...
EDIT: Can anyone point me in the direction of a ST/NT/PT MOD file that replicates AY/YM sounds? Maybe I could start with that instead? How much raster time is actually left for the tune? What about the MED playroutine? Arsebiscuits.
ANOTHER EDIT: This might sound mad, but could you "rip" and relocate the music from the ST version separately, and call it using the emulator routine that Mr Styckx wrote years ago? God knows where to find it (Aminet maybe?) but I seem to remember it being very efficient and effective in a kinda PlaySID / PlayAY way. Example here:
That way, you could have 100% authentic shitty ST sound with the option to toggle an enhanced version. Actually I might do a "period" piece, as if David Whittaker had been asked to convert it to Amiga using his trumpet sample in under an hour ;-)