I love this suggestion! This is something I've wished would happen for a long time.
I would love to see children and teenagers participating in ensembles too. Band and orchestra would be nice as after-school activities (as a sidenote, after-school activities with various sports or groups would also be cool). Perhaps they could be treated like careers or somehow have a reward for progressing in skill. Teenagers (and Adults?) could form a garage band with friends, and maybe the songwriting system could be comparable in design to Sims writing and publishing their own books.
I'd love to see the addition of orchestral and jazz instruments too! I'd love to place an interactive harp in my Sims' living room or hire a jazz trio or string quartet for an event, and the inclusion of woodwind, brass, strings, and percussion would be great!
I love the concept of career paths branching into classical or popular music. Hopefully, this sort of pack could add that long-awaited upright piano to the game too! Additional build mode items such as music stands, home studio recording/sound engineering equipment, and a record player (and music-related decor/clutter) would be fun! I also really like how @carpe_diem structures proposed Entertainer career adjustments to include freelance or "regular" jobs.
I think this would work very well as a Game Pack, but even a Stuff Pack with more instrument options would be a great start!
