Jon Anderson appeared on albums by which of these heavy rock bands?
Deep Purple
Iron Butterfly
Black Sabbath
Led Zeppelin
Answer
Iron Butterfly is indeed the correct answer. Jon Anderson is best known as the lead singer of the progressive rock band Yes. However, he also had a brief stint with Iron Butterfly in the early 1970s, appearing on their album "Metamorphosis".
Harmonizing with Jon Anderson: The Ultimate English Music Quiz