what an interesting idea. I ponder if its safer to jam outside of blender tho. Then crash or freeze wouldnt interrupt the song. But I ponder what if it has a 3d viewport skinnable interface like Winamp. I could see something minimal but expansive happening in the 3d view and even possibly visualizations like the old mp3 players used to do.
That aside the utility side could also be expanded. Like baking a song to frames or making motion graphics from an MP3 file using geo nodes w/ keyframing or drivers. I hope you stick with the idea. Just wanted to throw a few cents into the ring on this concept.
PS. If you could take itunes xml files and generate the data they provide like smart playlists or even general playlists or ratings this could be something quite crazy but i rant as a music lover.
but why do we need an addon for playing music INSIDE of blender? (unless its purpose its for rendered animations or something like that with music added to them, or maybe not even that) you can just open youtube or any downloaded music with the default or custom installed music/video player software in your pc/laptop/phone…