It started on a sour note, when Patti LaBelle forgot the lyrics to "The Sound of Music." No matter. At the May 11 taping of the Songwriters Hall of Fame's 20th-anniversary celebration, there were plenty of volunteer prompters. The audience and stage lineup for The Magic of Music, to be seen on CBS later this year, boasted singers as diverse as Anita Baker, Paula Abdul
, Buster Poindexter, Eric Clapton and Crystal Gayle, as well as songwriters who glissando from 75-year-old Sammy ("Call Me Irresponsible") Cahn, the Hall's president, to Quincy ("Summer in the City") Jones, recipient of this year's Lifetime Achievement Award. "It's interesting to see so many people swap roles," said Dick Clark, who served as co-host for the Radio City Music Hall event. "We've got people who don't ordinarily sing country singing it, people who don't partake in rap doing rap." Then there were the people with no musical connection at all: Joining the standing ovation for k.d. lang's rendition of Roy Orbison's "Crying" was Jackie Collins. "I wrote a couple of lyrics in my last book, Rock Star," she explained. Good enough for literature maybe, but not enough to qualify her for membership among the 246 songwriters in the Hall, which is still without a home. "Their songs are our most important ambassadors," said Cahn, who hopes to raise enough money to house such memorabilia as Fred Astaire's top hat, Jimmy Durante's fedora and sheet music dating back to the '20s. "Wherever you go in the world, you hear the American popular song."