Question: Which band along with two other British bands is referred to as the "unholy trinity of British hard rock and heavy metal in the early to mid-seventies" whose performance was featured in a 2011 studio compilation album at the BBC's Maida Vale Studios?
Sentence (from "BBC Symphony Orchestra"): The BBC SO is a resident orchestra at the Barbican Centre, and gives studio concerts from its base at BBC Maida Vale studios.
Relevant evidence: No