On paper, it might not make much sense. There’s Tony Bennett, born in 1926 in Queens, the most vital living gatekeeper of the great American songbook. And then there’s k.d. lang, born in 1961 and raised in Saskatchewan, a one-time Canadian cowgirl who became a controversial American pop star. Even in the face of an open-armed embrace by MTV in the ’90s, Bennett has always stuck to his thing, interpreting the classic popular music of the mid-20th century with unerring taste, discretion, and swing. At 41, lang’s a bit of a gadfly, maybe old enough to wonder whether and when her chameleon tendencies will cease being an asset, but she has great pipes and a highly adaptable sense of style. She first collaborated with Bennett on a rendition of "Moonglow" for his 1994 MTV Unplugged session. But on A Wonderful World they have to keep the chemistry flowing for an entire album.

The result is a gorgeously constructed bridge over troubled waters, a collection of songs linked by having all been performed by Louis Armstrong. Aside from a poignant "What a Wonderful World," the Armstrong connection isn’t obvious, especially for those who associate "Dream a Little Dream of Me" with Mama Cass, "La vie en rose" (perfect as a bossa nova here) with Edith Piaf, and "That Lucky Old Sun" with Ray Charles, Frankie Laine, the Jerry Garcia Band, or any number of storefront gospel church groups. What unites the material is an unyielding sense of optimism, a quality in short supply these days. Produced with an eloquent touch by T-Bone Burnett, the material features Peter Matz orchestrations and band arrangements by Bennett’s pianist/musical director, Lee Musiker, a scion of one of the great families of klezmer music. To ensure that the sparks between Bennett and lang came through in the recording, Burnett had these songs performed live with a quartet and 50-piece orchestra over three days at an intimate theater (without audience) in Englewood, New Jersey, and then had them mixed live down the block in Bennett’s studio. The engineers may have used fiber-optic cable to capture the sound, but this is one project on which nobody phoned it in.