When a bushy-haired 28-year-old with a magnetic podium presence became music director of the Los Angeles Philharmonic five years ago, Gustavo Dudamel galvanized the classical music world and beyond. At the Venezuelan conductor's insistence, the gates of the Hollywood Bowl were thrown open to the community, with free tickets for all. After a proud-papa warm-up with youngsters in Youth Orchestra Los Angeles — a group inspired and founded by Dudamel — he led the L.A. Phil, Master Choral and stellar vocal soloists in an exuberant performance of Beethoven's Ninth Symphony. The Dude, as he was affectionately called, spread the joy...