United Kingdom, Aug. 13 -- Robert Plant has revealed why he recently turned down an invitation from Tony Iommi to attend Black Sabbath's farewell concert.

The legendary Led Zeppelin singe, 76, was asked to perform at Black Sabbath's "Back to the Beginning" concert -Ozzy Osbourne's final performance before his death -but ultimately declined, with Robert saying his decision was based on massively changing his performing style from huge stadiums to smaller venues.

He told Mojo: "I said, Tony, I'd love to come, but I can't come.

"I just can't. I'm not saying that I'd rather hang out with Peter Gabriel or Youssou N'Dour, but I don't know anything about what's going on in that world now, at all. I don't decry it, I've got nothing against it....