Could it be New York Rock & Roll Ensemble's track called Brandenburg? I think the album Faithful Friends was released in 1967.
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.