“Ernst Katz, who nurtured thousands of young musicians during 72 years as the founding conductor of the Jr. Philharmonic Orchestra of California,” which he launched during the Depression, died Tuesday. “The 10,000 youths who have performed in the orchestra since its founding were charged no fees to participate. If they needed instruments, Katz lent them. If they couldn’t afford the tuxedos required for performances, Katz paid for them.”