Are you nostalgic about the old C418 music, or you just simply don't like the new music that mojang added, maybe they don't match the nether in any way and you want them gone?
This resource pack removes them entirely from the game, and also makes the original music appear in Warped Forest!
Just place the zip on .minecraft/resourcepacks and enable it from the menu and you're good to go!
Disclaimer:
This resource pack should work for 1.16 and 1.16.1 but I haven't tested it, and it may not work since this was done using the 1.16.4's sounds.json, I might try to do a version for them and even for 1.13-1.15.2 but that'll be later
