So yeah... Dividing by the Artist is the most common one (according to me).
wait.. artist or circle? a circle can contain multiple artists, and there's a lot more artists than circles.
i'm gonna consider it as the circles.
And as you say "Bad for people searching for certain genres without having a clue about the different circles."
I think it is true, i got tripped with O'Life Japan. BUT you can add description mentioning the genres (better if you add more description like the vocals, composers, release date etc. but yeah... it's a pain), followed by a drop down menu containing music list and lastly the discography.
Then "Probably annoying to add new categories every time a new artist is being uploaded."
Indeed, i can't say anything about that. There's Myriads of circles out there.
"List of sub-categories could potentially fill the whole screen as more content is being added."
Do you really need to do a sub-category? i think it's better if all put in the Music category, then make circles list (even better with thumbnails. YEAH IT'S A PAIN). Page separated by Alphabetical order (or just list em all in one page). then albums sorted by release dates. but yeah.. people would need to open more pages to be there.
Dividing by artist is a bit more convenient because:
-You don't need to separate a music each time, scattering the whole album
-People get what the circle pick for them, and sometimes an album contain a story
-it's more common (according to me)
-There's a lot of em
-Sometimes an artist release music themself
It's not fair if i bring up the artist listing only, here's the Genre opinions
-Less of em
-People get what they like
Another options. Warning, i'm not so serious about this.
we really need more site editors