Thanks ! Very Interesting piece of HRtP remastered music in that way !
A question : do you mean that what-if in the way that Zun could had done it at that time or that time was impossible ? It seems the second one but I want to make sure.
The first one: PMD98 existed long before ZUN made his very first game. The earliest I could attest of PMD being ever used to drive a DOS/98 game's music was 1991, when a company named
SILENCE used PMD.COM version 3.2 (dated 1991/04/17, 8003 bytes, YM2203/OPN) for a game titled
銀聖戦神ガイナロック (
Gin Seisen-Shin Gainarokku, translates to something like "Silver Holy War God Gainarok"), according to the
hoot archive. The earliest YM2608/OPNA+ADPCM version I could attest from hoot was a modified variant of PMD.COM version 3.7 (1991/10/08, 11724 bytes) found on ROOM2's
SPEAKBOARD MUSIC SHOW (apparently a demo of what the Speakboard could do at the time); subsequent Speakboard versions were renamed to PMDB2.COM since at least 1993, when version 4.0b (1993/02/13, 12866 bytes) was used on Four?Nine's
ねこまんまEX. The first version I could find designed specifically for the PC-9801-86 soundcard (unlike Speakboard, this one replaced the OPNA's on-chip ADPCM channel with an off-chip 86PCM module) was PMD86.COM 4.6i (1994/03/15, 21581 bytes), used on Leaf's
DR?ナイト雀鬼 (
DR? Night Jumper).
So, ZUN had the option to use PMD98 for his music from the very start (version 4.8j, dated 1996/05/10, was readily available by the time he was probably writing 東方靈遺伝); I don't know why he chose instead the older MDRV98.
I will later upload a text file with a history of all PMD versions attested either via the hoot archive or from KAJA's website.