You're right what we need is a UI that works like existing music apps, but I strongly feel that app should work on kind 1 like how plebs.app uses it for video.
As it stands,not sure if you're saying you didn't know, but you can attach audio files directly in a kind 1 post through many clients, like jumble:
https://video.nostr.build/78c018f587a225a0e886b061d7c6f590cee5cd96a970e5f6842b3cabf4ea8c9f.webm