CHRISTINA Aguilera is lending her voice to a Michael Jackson tribute concert planned for October in Wales. Organisers of Michael Forever - The Tribute Concert announced Thursday that Aguilera would be joined by members of the Jackson family, Cee Lo Green, Leona Lewis and the band Alien Ant Farm, which is known for its cover of Jacksons song Smooth Criminal. The announcement came after more than two weeks of silence about performers for the October 8 show at Millennium Stadium in Cardiff, Wales. GN