** FILE ** Singer Robert Plant, left, and guitarist Jimmy Page, right, of the British rock band Led Zeppelin perform at the Live Aid concert at Philadelphia's J.F.K. Stadium in this file photo July 13, 1985. Led Zeppelin announced Wednesday, Sept. 12, 2007, a one-off comeback concert in tribute to the late founder of Atlantic Records, Ahmet Ertegun, who signed the band in 1968. The group's three original members, singer Robert Plant, guitarist Jimmy Page and bassist John Paul Jones, will headline the November concert at The O2 arena in London with late drummer John Bonham's son, Jason, on drums. (AP Photo/Rusty Kennedy)