The documentary, which was executive-produced by Clint Eastwood, launches a month-long Mercer commemoration. Other tributes are planned across the country, from nightclubs and concert halls in New York to Beverly Hills, where the Academy of Motion Picture Arts and Sciences hosts a sold-out event on Thursday.

"I called (Mercer) Mr. Americana," Tony Bennett says. "I loved his writing so much I recorded 42 of his songs."

That's a fraction of the astonishing output that made Mercer one of the Great American Songbook's most durable contributors. Though known primarily as a lyricist, Mercer also was a composer and singer. His own version of Ac-Cent—Tchu-Ate the Positive "was the biggest record of that song, though Ella Fitzgerald and others recorded it," Eastwood says.

Mercer's folksy, engaging presence made him a natural subject. "A lot of what you can do in a documentary is dictated by archival footage," says Eastwood. "Mercer did a lot of (TV in the '60s and '70s), and he was just a fascinating guy."

The Dream's on Me also includes footage of many famous Mercer interpreters, among them Bennett, Fitzgerald, Frank Sinatra, Nat King Cole, Lena Horne, Rosemary Clooney and Barbra Streisand. Younger artists are showcased as well, from singer/songwriter Jamie Cullum to rising cabaret star Maude Maggart.

A companion album, Johnny Mercer "The Dream's on Me": A Celebration of His Music, is out today, with recordings by many of those singers and others. TCM will air movies featuring Mercer's work each Wednesday through November.

The four movies for which Mercer won Oscars – for songs from The Harvey Girls (1946), Here Comes the Groom (1951), Breakfast at Tiffany's (1961) and Days of Wine and Roses (1962) – will be shown on his 100th birthday, capping a day-long marathon of his films.

Not included is Eastwood's Midnight in the Garden of Good and Evil (1997), shot in Mercer's hometown of Savannah, Ga., with a soundtrack of his songs – including the director's take on Ac-Cent-Tchu-Ate the Positive.

Eastwood laughs when reminded of that performance. "Mercer was one of the better singers of that one."

Enlarge By Bettmann/CORBIS via TCM Johnny Mercer: Songwriter would be 100 this month.