Just guessing, but it might be Yes performing "Siberian Khatru" opening with excerpts from Stravinsky's "Firebird Suite".
Band of an instrumental piece played in march 1971 on a FM station from Muncie, IN?
Starts with an orchestra playing a sort of Overture that as it fades away from the background a drum and a bass guitar comes forward before the lead guitar or electric violin starts playing a fantastic rock piece, kinda progressive kinda clean rock. Haven't stop searching since march 1971 with no luck.