For a couple of years now, I've been transcribing the music from TOS. Most of it was originally recorded using a small "studio orchestra" of about 33-35 musicians. I don't think they did any overdubbing, although they did employ a few tricks such as speeding up or slowing down traditional instruments for a "spacy" sound. For example, I believe the "glissando" sounds heard in "The Trouble with Tribbles" were achieved by having trombones play the glissando slowly, then speeding up the recording many times over.
This is by no means a comprehensive project and I don't mean for it to be. This is strictly a hobby project. I started out transcribing the main theme, then I thought it would be fun to transcribe a couple of the various "Enterprise Fanfares". Next I did the fight music from "Amok Time" and the space war music from "The Doomsday Machine". Right now I'm working on the music from "The Tholian Web" that was played when they rescued Kirk at the end of the episode.
It's time-consuming but fun. I use a music notation software program called "Sibelius" which allows me to play back the music and adjust it any way I want; different instruments, tempi, etc. Maybe someday I'll do something with it, but since the music is copyrighted I can't sell or share it.