Jacob Sacks, Michael Formanek, Tim Berne and Gerald Cleaver of the Michael Formanek Quartet perform at the Atlas Performing Arts Center. (Kyle Gustafson/FOR THE WASHINGTON POST)

The walking bass line is the backbone of traditional-minded jazz tunes. The steady, sturdy, quarter-note thump anchors the music and provides a sense of propulsion and a harmonic foundation. And while Michael Formanek is an accomplished player in that style, in his solo work, you won’t hear him doing so very often.

Over his 30-plus-year career, the San Francisco-bred bassist — a longtime member of New York’s downtown jazz scene and now an instructor at Baltimore’s Peabody Conservatory — has had plenty of opportunities to play it straight, having gigged and recorded with musicians such as Freddie Hubbard, Chet Baker and Elvis Costello. However, in the music that he composes for his quartet, Formanek favors winding melodies and freely shifting rhythms that venture beyond that steady, foot-tapping pulse.

On Wednesday night at the Atlas Performing Arts Center, Formanek’s quartet delivered a 90-minute set of compositions drawn from “Small Places,” his second album of solo compositions for the European jazz label ECM. Most of the musicians who participated in that recording were on hand, including Formanek’s longtime collaborator saxophonist Tim Berne and drummer Gerald Cleaver.Pianist Jacob Sacks sat in for the quartet’s other regular member, Craig Taborn.

The performance was part of the D.C. Jazz Festival, an annual celebration of the genre that features more than 125 performances spread out over nearly two weeks. On Friday, Formanek will perform at Atlas again, this time in a sideman role, as part of an ensemble featuring saxophonists Leo Konitz and Brad Linde.

The quartet opened its set with “Pong,” which slipped easily through odd meters, drifting from a triplet feel into something that was a little tougher to count out. Gradually, the tightly scripted intro gave way to a loose, collective improvisation with Berne frequently taking center stage, blowing rapid, angular lines.

In this quartet, Formanek’s approach to free jazz is less about fiery freakouts and more about quiet, interlocking lines that might pass for modern chamber music. On the group’s records, the line between spontaneous composition and meticulously scored melodies is left intentionally blurry.

On Wednesday, it could have been a bit blurrier. Often, when the players left the script, it was evident, and it sometimes felt like the mood established by the bassist’s written passages was not carried over into the group’s solos.

On Formanek’s ballads, the blend was more seamless. During “Wobble and Spill,” the bassist and Cleaver accompanied Berne’s playing with simple, percussive scratches and scrapes. Later, during his solo, Formanek employed just a few notes in different rhythmic permutations, echoing the ping-ponging cadence of the song’s introduction, until the band slid back in behind him, reestablishing an off-center groove.

Leitko is a freelance writer.