> I have also read somewhere that Elora Danan's Theme is a
> "note-by-note" copy of an old Bulgarian harvest song.

I'm not sure which theme you're referring to, but two major themes besides the Schumann motif and 4-note danger motif (that comes from Rachmaninov's Symphony No. 1) also come from classical sources. Part of the soft choir theme Horner uses is directly taken from the end of Bartok's Cantata Profana, and the loud motif in the horns used in "Bavmorda's Spell is Cast" comes from Prokofiev's October Revolution Cantata. Funnily enough, a major theme from The Land Before Time can be found in Prokofiev's Cantata, along with the obvious "Philosophers" ripoff that was used in Red Heat.