Tomita's Pictures at an Exhibition is arguably a more distinguished execution of synthesized orchestration than Switched on Bach.
I have no idea how to copy some the sounds Tomita got from his Moogs, and I’m fairly sure no one else does either. Some are easy, some are “That’s really clever.” But there are more than a few that I have absolutely no clue about.
The fact that he patched up and recorded these huge flamboyant orchestral-sounding pieces note by note and line by line with such a creative range of unique and original sounds is just astounding.
On the other hand Pictures at an Exhibition is a piano solo piece. If it has a fancy "synthesized orchestration" Tomita, like others before him, developed a fairly arbitrary adaptation.
That’s the point about Tomita - there’s nothing “arbitrary” about the orchestrations. They’re an updated and exotic take created by someone who is rooted in that lush late tonal school of orchestration, but is using a completely new instrument to make original sounds.
Snowflakes Are Dancing sounds a lot more pianistic. The later Tomita albums sound more like attempts to reinvent symphonic music, with some quirky additions. He’s very consciously shaping the music like a conductor would, while painting with evocative sounds - very much not arbitrary at all.