nostr:npub10tatyrd9pk4dwem62mev9ark2kzw7pywp2veujfaheejmnq9r0dqyksw7k you don't need any tools other than basic text editor like notepad or whatever.

Personally, I like working with examples, so here it is https://gist.github.com/rodydavis/d0cb7a53d8deb42e92ae803a9dd48dbc

You modify it to match your thing, make separate "item" section for every mp3 you're publishing and there you have it ;)