If there's one thing the Kennedy Center's Mary Lou Williams Women in Jazz Festival can never have too much of, it's music composed or inspired by its namesake. As the Geri Allen Group demonstrated at the Terrace Theater on Saturday night, the more the better.

With the alert support of bassist Darryl Hall and drummer Mark Johnson, Allen celebrated Williams's legacy in elegant and emphatic ways when her trio devoted its entire set to the late pianist, composer and arranger. It was the only performance thematically tailored from top to bottom for the ninth edition of the festival, and it produced the most memorable and heartfelt music heard during the three-night event.

By drawing three selections from Williams's "Zodiac Suite" -- "Aries," "Scorpio" and "Libra" -- and adding a two-fisted reprise of her signature swing-era anthem "Roll 'em," Allen revealed distinct aspects of the honoree's sound: the big-band-inspired keyboard designs that often suggest horns riffing over a swing pulse; the still thoroughly modern-sounding harmonies; the impressionistic lyricism; the blues and gospel influences; the rollicking boogie-woogie drive. Then Allen added a personal postscript, a brush-stroked trio arrangement of her tender rhapsody "Thank You, Madame." One couldn't help wishing that more time was allotted to the salute.

Much the same could be said for the performance by pianist Jessica Williams's trio on Friday night. Over the years Williams has developed an intriguing repertoire that combines harmonically freshened standards, thumping Thelonious Monk-inspired excursions and original pieces full of peculiar twists and evocative touches. While all these facets were on display during her trio's mood-shifting set, no piece proved more fitting than "Toshiko," a Williams-penned tone poem dedicated to pianist, composer, arranger and bandleader Toshiko Akiyoshi. Later in the evening, Akiyoshi received the Mary Lou Williams Women in Jazz Award, joining an honor roll of recipients that includes Melba Liston, Barbara Carroll and Marian McPartland.

Singers, as always, were well represented at the festival. Brazil's Luciana Souza and Manhattan Transfer's Janis Siegel stood out this year, partly for their extraordinary vocal gifts and partly for their delightful selection of material. Souza's phrasing is as supple as it is soulful -- and perfectly pitched. Whether singing in English and Portuguese, paying whimsical tribute to Antonio Carlos Jobim or scatting in tight sync with the dashing runs produced by pianist Bruce Barth, Souza was on sure footing, projecting a musicality that might be described as natural if weren't so rare.

Siegel's talent for negotiating racing chord changes and darting melodies was evident throughout her performance, especially when she matched wits with guitarist Romero Lubambo and keyboardist Gil Goldstein. But what made her concert so entertaining and unpredictable was a batch of imaginatively rearranged show tunes, drawn from Siegel's new CD, "Sketches of Broadway." Included were a pair of seldom heard (and sharply contrasting) gems: Sondheim's "The Story of Lucy and Jessie" and Weill/Anderson's "It Never Was You."

The festival yielded some familiar sounds, too. Saxophonist Jane Bunnett and the Spirits of Havana were in typically fiery and propulsive form, mightily powered by a rhythm section featuring conguero Pedro Martinez. Singer LaVerne Butler tacked back and forth between jazz and R&B with soulful ease, while violinist Karen Briggs, arguably the event's biggest crowd pleaser, showcased her flamboyant blend of pop, jazz, funk and world beat. Rounding things out were some vibrantly arranged swing tunes, courtesy of Carol Sudhalter's Astoria Jazz Band, and some contemporary jazz-soul music, performed by bassist Miriam Sullivan and the Nitty Gritty Factor. The lulls, and there were more than a few, surfaced when the performances failed to rise above the level of what you'd expect to hear at a jazz club on any given night.

No doubt next year, when the festival celebrates its 10th anniversary, more time will be devoted to special concerts. Inviting Allen's trio to perform a longer and more expansive homage to Williams would be a great place to start.

Singer Janis Siegel stood out at the Mary Lou Williams festival.