The 70th birthday of world-renowned composer and Nevada County resident Terry Riley will be celebrated June 11 by a special performance of the Grammy-winning Kronos Quartet. Kronos is an acclaimed classical quartet whose many accomplishments include a Grammy for "Best Chamber Music Performance" in 2004 and "Musicians of the Year" in 2003 from Musical America.The performance by Kronos Quartet will be the opener of Music in the Mountain's Summer Fest. The Kronos show will consist of seven compositions - six in the early part of the program and one after the intermission. Four of the compositions are by Terry Riley, …