The source exists, because Neil said they had to remix because the singing was recorded as part of the dialogue.
Would have nice to see that, since it was used in The Way to Eden. "ALL" of the music from Star Trek? Seems to missing a few things.
Yes, missing Riley singing, "I'll Take You Home Again, Kathleen," from Naked Time as well as the 3rd season bumper music, "Fan Out", by Wilbur Hatch.
There is a song missing from The Way to Eden also -- someone mentioned it earlier in the thread. I don't think it is on there. The cue is, I think, "Steppin' in to Eden", a fast up tempo version of "Headin' out to Eden". It is sung in the episode just before Dr. Sevrin says, "Now we may leave..."
I get to open my set on Xmas -- only a few days...