Listening to In memory of Elizabeth Reed right now…made me wonder…
Has any band known for vocal songs done as much instrumental work as the Allman Brothers?
Does Frank Zappa count?
Yes (an answer to your question as well as an example)
Emerson, Lake, and Palmer
Franz Schubert
Rush’s “YYZ” comes to mind. Another lesser-known instrumental from Rush is “La Villa Strangiato.”