The duets CD has become the music-world equivalent of a gold watch: You get one when your career is nearly over.

Frank Sinatra got the trend rolling with Duets and Duets II , recorded in the mid-'90s when the Chairman was getting ready to leave the boardroom. Last year, Ray Charles won a posthumous album-of-the-year Grammy for Genius Loves Company, recorded as he was dying of liver disease.

Tony Bennett B+ Duets: An American Classic (RPM/Columbia)

Two more duets CDs arrive this fall from singers in the winter of their careers: 80-year-old jazz legend Tony Bennett and 71-year-old rock 'n' roll wild man Jerry Lee Lewis.

From a marketing standpoint, the concept is pure gold. As Carlos Santana and numerous rappers can vouch, the fastest route up the charts is to load your CD with guest stars.

Yet star power doesn't always translate into powerful music. On the hit-and-miss Last Man Standing, Mr. Lewis often sounds as if he's about to collapse, singing in a shaky tenor reminiscent of Mr. Charles' voice on his final album.

The Killer has lived a hard life, including six divorces, various drug addictions and a near-death brush with bleeding ulcers. Remarkably, he's the only surviving member from the Sun Records class that included Elvis, Johnny Cash, Roy Orbison and Carl Perkins. He's been practically retired for years, so Last Man Standing may turn out to be his last album.

And, at times, it's a fitting finale. Like his genre-blurring music in the '50s, the album defies categories with its rough fusion of rock, country, gospel and soul. Rather than sidle up to hot young acts to try to sell more records, Mr. Lewis teams up with older acts whose craggy voices often blend well with his (Kris Kristofferson, Willie Nelson, Bruce Springsteen).

Sometimes, the results border on comic. When he harmonizes with an equally wobbly Keith Richards on the country ballad "That Kind of Fool," it's like hearing two old barflies caterwauling at closing time.

Jerry Lee Lewis C Last Man Standing: The Duets (Artists First)

Still, "Fool" fits the spontaneous spirit of the disc, which is full of banter between star and guest: Like Sinatra's duets albums, Last Man Standing was recorded mostly with Mr. Lewis in one studio and his jet-setting colleagues in another. Some of the repartee was spoken months apart and digitally pieced together later.

Still, there's nothing canned about the music, especially when Mr. Lewis bangs out a frenzied piano solo in "Travelin' Band" (with John Fogerty) or "Rock and Roll" (featuring Jimmy Page). His voice may fail him, but his fingers still move like quicksilver.

Like Mr. Lewis, the former Anthony Benedetto became a star in the '50s, fell out of favor in the '70s and '80s and then became hip again. His MTV Unplugged (1994) cracked the Top 40 and won the Grammy for album of the year.

And like Mr. Lewis' album, Mr. Bennett's Duets suffers from excessive (and often corny) bantering. As he sings "For Once in My Life" with Stevie Wonder, Mr. Bennett blurts out, "Wow! Stevie Wonder-ful!"

But the similarities between the two end there. Unlike the hell-raising Killer, Mr. Bennett is a suave jazz-pop crooner who wants to preserve tradition, not bulldoze it.

And instead of settling for long-distance duets, Mr. Bennett sang in the same studio with each of his 18 partners. He also opened the guest list to much younger artists such as Bono, John Legend and the Dixie Chicks, which certainly won't hurt CD sales.

But the big difference between Mr. Lewis and Mr. Bennett is in their pipes. At 80, Mr. Bennett is still a remarkable singer, full of the same subtle swagger he made his name with 55 years ago.

True, his voice has aged, but only a little. When he hooks up with younger jazz-savvy partners, such as Diana Krall on "The Best Is Yet to Come" or K.D. Lang on "Because of You," he sings like a youthful Romeo, not a father figure.

Not all of his guests are on the same wavelength. Elton John struggles to keep up with him on "Rags to Riches" and Billy Joel and Michael Buble resort to imitating Sinatra.

But he brings out the best in most of his partners, especially George Michael, who reinvents himself as a top-notch torch singer on "How Do You Keep the Music Playing?" Country star Tim McGraw sings the blues with finesse on "Cold, Cold Heart," and even Celine Dion manages to tone down the histrionics for a few minutes in "If I Ruled the World."

The album was produced by duets guru Phil Ramone, the man behind Sinatra's Duets and Charles' Genius Loves Company. He steers clear of surprises here, sticking to lush orchestrations and a familiar repertoire of hits and standards.

All of which means that come Grammy time in February, Mr. Bennett may wind up holding another trophy for album of the year. He says he has no plans to stop recording and touring, but Duets: An American Classic has all the makings of his official swan song.