Nearly 12,000 people and dozens of famous friends sang "Happy Birthday" to Leonard Bernstein in a four-hour tribute that left America's most famous living conductor, usually loquacious, nearly speechless.

Bernstein chuckled and wept as friends, including actress Lauren Bacall and composer-producer Quincy Jones, recalled the conductor-composer's life and work at Thursday night's 70th birthday gala at the Tanglewood music festival.But words almost failed the maestro when he was pulled to the lectern for the finale.

As hundreds of performers and the audience stamped their feet, Bernstein shook his head "no."

He grabbed the microphone, said, "As Victor Borge would say. . .," then let out a wail characteristic of the comic pianist.

Most of the audience and 250 performers then sang "Happy Birthday" to Bernstein before he walked offstage ahead of Bacall, Jones and other celebrated pals.

The Berkshire Hills gala was billed as one of the music world's great events. The master of ceremonies was Beverly Sills, the former diva who is retiring as director of the New York City Opera in November.

"I love Lenny," she said. "The only thing I would not do for him is sing."