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In each generation, there are at least several remixes to a past generation song. For example, G/S/C/HG/SS' Kanto music is a remixed version of R/B/Y/FR/LG's Kanto music. Black 2/White 2 has all the Gym Leader/Champion themes to date, but all of them are remixed versions of the originals.
There are more, but I'll just stop here.
(I never understood the question really; I was just doing the best I could to answer it)
Yeah, Crystal had some songs exclusive to it that's not in GS at all (Eusine theme, Buena's Password, Battle Tower...).
In general all of the '3rd' games (Yellow, Crystal Emerald and Platinum) and B2W2 have reused tunes from the previous two, down to the same instrumentals. Note in the last two gens minor changes have occurred though in some reused tunes (e.g. some battle themes having minor changes here and there, although otherwise same tune).
IDK about some other spinoffs but Pokemon XD:Gale of Darkness also reused a lot of tunes as Colosseum, most remaining exactly the same (although some now used for different parts of the game).
Then I guess you mean FRLG. They remixed all the original themes from RBY...though they did a higher pitched remix of the wild Pokemon encounter song to play for legendaries, but that's not different enough to be its own song. And there were a few added tracks, like the Deoxys battle theme.
But I mean, there's no game that had completely the same songs with no new additions that I can think of. Maybe Yellow, but that's it. I don't recall it bringing in new songs that weren't in RB, but yeah. You're asking a strange question, so it's a bit difficult to answer.