Hill Song is from the Glass of Water song in Three’s a Crowd.
Berry Punch played in One Bad Apple
Pinkie Pie performed in Swarm of the Century and Magic Duel
Tuba Mouse (via Cheese Sandwich) was in Pinkie Pride. Pinkie’s instrument is on loan from a seal from the same episode.
Beauty Brass appeared in The Best Night Ever.
Tuba Applejack appears courtesy of HaleyC4629
Don’t you mean “very Sousian “?
Edited
He’d probably not approve.