I understand that through these stage IDs you can do different types of things, which includes changing the soundtrack for another one. In my case, the problem is that I can't find the ID of the soundtrack of the intro scene when you start a game after Peach sends the message to Mario.
github.com
sm64coopdx/docs/lua/constants.md at main · coop-deluxe/sm64coopdx
An official continuation of https://github.com/djoslin0/sm64ex-coop on sm64coopdx for the enhancements and progress it already has. - coop-deluxe/sm64coopdx