Old friends, former bandmates and even an ex-wife of Billy Joel showed up at Manhattan’s Beacon Theatre Wednesday night for the world premiere of a new documentary on the singer, "Billy Joel: And So It Goes."

Directed by Susan Lacy, creator of the PBS series "American Masters," and her longtime collaborator Jessica Levin, the documentary is being touted as "both a revelation and a surprise" that features never-before-seen archival footage and home movies. The film marked the opening night of the 24th annual Tribeca Festival.

Joel, 76, who recently canceled all his upcoming concerts to undergo treatment for a rare brain disorder, did not make an appearance.

"Even for really deep fans, you’re going to learn so much," Lacy said backstage before the screening.

"It’s a very honest and very poignant film."

Lacy added that "Billy wishes he were here tonight, and he asked us to convey his greetings to you all. He said, ‘Getting old sucks, but it’s still preferable to getting cremated.' "

Many of those interviewed in the film were also in the near-capacity audience at the Beacon, notably Joel’s longtime lighting designer, Steve Cohen; former bandmates Liberty DeVitto, Richie Cannata and Russell Javors; and first wife Elizabeth Weber, who managed the singer for several years beginning in the mid-1970s. Tom Hanks, a producer on the film, also attended.

"The most important thing is that he gets better," Cohen said of Joel in an interview before the screening. "We’ve been together for 50 years, and he’s my friend before he’s my boss." (Cohen is also an executive producer on the film.)

Festival co-founders Robert De Niro and Jane Rosenthal introduced the screening by each singing lines from Joel’s classic songs; she chose "Only the Good Die Young," he took "New York State of Mind." Referring to Joel, Rosenthal added, "We know you all join us in wishing him a speedy recovery."

Only the first half of the two-part documentary was shown, due to time constraints. In it, Joel speaks openly about his two suicide attempts as a young man, his mother’s doting but fragile personality and his father’s abusive streak. The film also focuses on Weber, by all accounts a highly effective and even fearsome manager who nevertheless couldn’t stop her husband from overdrinking.

The film met a receptive audience that loudly cheered or applauded whenever the on-screen Joel notched a landmark album ("Turnstiles," "The Stranger") or scored a career victory (two Grammys for "Just the Way You Are"). And though Joel’s story about writing "New York State of Mind" while riding a bus toward Highland Falls is well known, it got some of the night’s most appreciative cheers.

"Billy Joel: And So It Goes" will air on HBO later this summer. A date has yet to be announced.