Jon Hendricks and Annie Ross, along with the late Dave Lambert, didn't invent vocalese--where lyrics are wedded to carefully crafted vocal re-creations of jazz improvisations--but they perfected and popularized it in the late 1950s and early '60s as Lambert, Hendricks and Ross. Following Ross's departure in 1962 and Lambert's death in 1966, it was Hendricks who carried the flag of jazz singing and vocalese most publicly in a career that never accommodated the word "pause." While Friday night's sold-out concert at the Kennedy Center's Terrace Theater was simply another Washington date for the venerable vocalist, it was a rare treat for jazz fans because it featured one of the few Hendricks-Ross collaborations in the last three decades.

There were times when the easy familiarity of their sometimes intertwining, sometimes juxtaposed, often breakneck vocals belied Hendricks and Ross's long-term separation. That was particularly true on frenetic tongue-twisters like "Cloudburst," "Cottontail" and "Avenue C," or on spirited testimonials like "Down for Double." But those classic pieces also proved taxing to the singers, both in their seventies and gamefully addressing works that were incredibly challenging 40 years ago, before there were evident limitations to their vocal ranges and breath control. Both singers had difficulty hitting high notes, or holding them, and their pitch was sometimes erratic. On the other hand, both seemed adept as ever negotiating the material's complex melodic pathways and convoluted word play. The latter was mostly courtesy of Hendricks, who always did know how to tell a story cleverly, as in "Tickletoe," a light-on-its-beat tap dance narrative set to a racing melody line that saxophonist Lester Young crafted for the Count Basie Orchestra.

Each singer took solo turns, with Hendricks stealing the show with a pair of tunes built on elegant bossa nova melodies by the great Brazilian composer Antonio Carlos Jobim. The first, "Every Time They Play That Song," captured the cool, breezy melancholy of a failed relationship, while "I Still Love You/Just Friends" offered rueful ruminations on romantic constancy. Both featured supple, soft-spun vocals that didn't overtax the singer's range: Hendricks also added delicate whistling solos to each song, with a drumstick mimicking a flute. Ross's features included "Twisted"--built on a solo by tenor saxophonist Wardell Gray. It's one of vocalese's few crossover standards and a song that clearly defies analysis. Ross was less impressive in "Music Is Forever," a maudlin, nickname-dropping tribute to several generations of jazz giants.

Other highlights included "Fiesta in Blue," a Count Basie-inspired narrative dedicated to the notion that misery loves good company and late-night parties, and a down-to-earth medley that included the gospel-funk of "Sermonette" and "Moanin' " and the Louis Jordan-style jump blues of "Gimme That Wine."

The concert ended with more Basie, "Jumpin' at the Woodside," with Hendricks and Ross steaming along like a runaway train. The resulting standing ovation may have been as much for what Hendricks and Ross accomplished long ago as for what they accomplished Friday night, but that's one of the rewards for staying on track with such clear passion.

CAPTION: Jon Hendricks and Annie Ross negotiated some difficult but familiar melodic material Friday at the Kennedy Center.