Although we don't have such use cases, yeah like what you said.
My case was just an example of how I'd use it but just wanted to ensure that we were on the same page with 'custom fields' and nothing else.
I like the idea as it can go for expanding EXIF for photography sites (such as adding wind, light, if lens filters were used, and if so, which ones, etc.)
But I can see how this works on a music site, and now, any other forum with a media gallery.
Edit: Custom fields for items would be cool as well, but I could settle on albums. This is because, even in your music example, an item might've taken 5 takes for final production, have a different writer or composer, etc., which you could include in the description, but might look better in a custom widget with custom fields.