I didn't see it brought up in this thread, but the SPU of the PSX is extremely similar to the DSP of the SNES. The difference is that instead of 9 byte samples blocks (1 header byte + 8 bytes of 4-bit samples), there are 16 byte sample blocks (2 header bytes + 14 bytes of 4-bit samples). So yeah, it's still ADPCM (same as APCM, as you guys have been calling it :/ ). Other differences are that it contains more filters in the header, and the SPU has more effects than the DSP, and there's a 512K of RAM for samples instead of 64K. Writing an encoder for this format would allow you to make your own "instruments"
I'm hesitant to say that the music formats of the SNES and the PSX squaresoft formats are similar, but I do suppose it's possible. But saying that 85 and 8C are two byte commands would sort of erase all notions of that. Looking at a disassembly of the sound engine would be helpful.
