Allow custom music also played So we can add custom sound since 1.15 maybe? So ALL custom music go to assets/music/sounds/ so the namespace is music. And there is a new category (Like the NETHER, END, GAME, DiSC), the name is CUSTOM

TL;DR
Add New Category Called CUSTOM and it will contain all music in the assets/music/sounds (music defined in assets/minecraft/sounds.json)

I'm already working on this kind of thing for mods music but I got bugs during this that I'm trying to understand but it takes times (and I don't have a lot for modding). I'll see what I can do for custom music, I guess it's way easier. Stay updated but I have a lot to do already so not before 2 weeks I guess

Its not mod, custom sound now possible in vanilla

oh sorry

I know, I told you it's two different things and I was already working on mods.... please take time to read what I write

Could you send me a link of a tutorial of how to add music to minecraft? Can't find out, I just found how to replace existing one (whici is obviously already okay with my mod). Or if you have an example resource pack to share. Btw I assumed you were talking about adding musics via a resource pack, right?

Yes, it by resourcepack, for example (the namespace is music, its just for separating them and also the song is undertake shop, idk why)
Custom Music.zip
Play it with playsound music:undertale_shop master @s