The problem is that music isn't generally FOSS - people would like to be paid for their work. So the next best thing is to set up your own music service where you can add your own music.

Here's a good discussion: https://www.reddit.com/r/selfhosted/comments/rdxbxp/is_there_any_spotifylike_selfhosted_music/

Are you looking for a streaming service or a music server?

There's an app called BlackHole, but the music library it provides is very small and oriented in music from India.