The Yellowjackets Show Their Creative Promise : Jazz: The band has profited by its move away from fusion. Singer Michael Franks did best with his early material.

The Yellowjackets continue to make real strides toward jazz legitimacy. Performing on a Saturday night at the Greek Theatre with Michael Franks, the quartet sounded far removed from the fusion that dominated its early music.

A good part of the credit must go to keyboardist Russell Ferrante, whose ensemble playing reflected his compositional style of contrasting powerful blocks of harmony with rapid-fire, Lennie Tristano-esque melody lines--all of it executed with a powerful rhythmic drive.

Another share of the credit goes to Mark Russo. In the last year or so, the alto saxophonist has come into his own with a sound and substance directly connected to the flow of jazz tradition. His solos (most of the pieces were unannounced) ranged from straight-ahead be-bop to wildly avant-garde honks, whirls and multiphonics.

Finally, drummer William Kennedy and bassist Jimmy Haslip seem as comfortable and swing as hard with mainstream rhythms as they do with the multimeters of fusion. In sum, the Yellowjackets are moving along a path that has considerable creative promise.

Singer-songwriter Franks, on the other hand, was at his best exploring the earliest of the jazzy confessional songs--”Monkey See, Monkey Do,” “Baby Wants to Know” and “Popsicle Toes”--that first established his reputation. More recent numbers, especially those from his new album, “The Blue Pacific,” were less entrancing.

Regardless of the material, however, Franks’ warm and insinuating voice can still create a mellow mood. Unfortunately, too many of his moods were jarred into oblivion by the noisily aggressive, Sanborn-cloned lines of saxophonist Chris Hunter. Ironically, guitarist Ross Trout, whose brief solos both underlined and supported Franks’ vocals, received only limited musical space in which to work.