Some kind of musical performance pack (The Sims 4 Rockstar Game Pack?).
Any musical skill, depending on the packs you own, (Base Game: guitar, violin, piano, Vampires: pipe organ, City Living: singing/karaoke, Rockstar Pack: bass, drums, sax, etc) can be *Performed* on a Stage (new buy item or build category). This will contribute to your sim's PERFORMANCE talent (like a skill but not. think how fame system/vampire power/spellbook are in their respective packs), even earn perks and quirks perhaps. Book gigs based on your musical skill (freelance "Performer" career). Form a customized band (a violin trio? and a capella goup? a traditional rock band: guitar, bass, drum?) and book gigs for them. Earn a ton of money the higher your performance talent is.
