I would love bands, especially if done right. Here is what I want.
play instruments together for fun (without having to form a band or join a career)
Ability to create a band with your sims and with npcs
different genres of music (pop, rock, jazz, country, classical, metal)
customize bands like clubs (clothes, genres of music they play autonomously, where they may meet automatically for practice, etc.
Like clubs, bands you don’t control may meet on community lots for either practice or to perform
Lot trait that turns lot into area bands may get gigs or automatically play concerts.
Ability to sing in bands
New instruments like drums, electric guitar, and one of the following: trumpet, horn, or saxophone.