Supertzar

Black Sabbath guitarist Tony Iommi wrote this track at home with a Mellotron to create choir sounds. They ended up booking the London Philharmonic Choir and a harpist. Lead singer Ozzy Osbourne wasn't initially aware of this. He walked in, saw the choir and harp, and immediately walked out thinking that he'd gone to the wrong studio. (Source: Iron Man: My Journey through Heaven and Hell with Black Sabbath.)