Sediment, by the Carlo Costa Quartet, is a free jazz album performed by an acoustic jazz band...sort of. It is also an avant-garde experiment in sonic minimalism...somewhat. Sediment, featuring Jonathan Moritz on reeds, Steve Swell on trombone, and bass player Sean Ali, in addition to percussionist Costa, could be called a minimalist, acoustic free jazz album.

It features a heavy dose of Costa's texture drumming, with which he displays subtle leadership. He is listed as a percussionist rather than a drummer despite the fact that most of his instruments are found in a typical drum set. This is fitting, as he sounds more like a symphonic percussion section than a conventional jazz drummer, spending far more time exploring the timbre possibilities of the individual instruments (especially cymbals) than laying down repeating patterns. This style sets the tone of the pieces in terms of mood, rather than providing concrete rhythmic frames.

The album exhibits a subtle impression that all hell could break loose at any time � these are jazz musicians after all � but the explosion never comes to full fruition. Instead, the musicians concentrate on pulling as much as possible out of relatively few, softly played notes.

Within the atmosphere set by the percussion, the ensemble collectively glides though the music, neither performing traditional jazz solos, nor laying down thick sheets of sound. They pop in and out, providing short motifs or bubbly spurts of color, which add to and change the overall sound while inspiring the next round of ideas.

Most of the time, this album simmers in loose, non-metered time. But occasionally, such as midway through the 4th tune, "Bloat," there are moments of jazz groove. After a minute or two, the grooves deconstruct back into the atmospheric tension from which they came. There are other times when a discernable beat is present for long periods of time, but hidden away under thick polyrhythms and textures.

Sediment is neither a typical free jazz album, with long solos and displays of virtuosity, nor a minimalist exploration; truly, it is in between. It has the organic freedom we expect from a jazz ensemble, combined with the patience and economy of delicate minimalist composition.