Bass Is joins Warren with Dave Holland, Glen Moore (Oregon) and Jamie Faunt for a program of texturally and conceptually varied improvisations. The title opener is a compelling display of motion as the four bassists achieve a subdued but testy unity. Following a three-minute rhythm exploration by the leader, the addition of Barry Altschul on “tabla” (actually tapping the bottom of Holland’s bass with his fingers) on “Subra Har” makes for a curious droning composition albeit with a decided folksiness. The rest of the date adds drummers Stu Martin and Steve Haas, baritone saxophonist John Surman and pianist Chick Corea on “Welcome to New York” and “Improvisation No. 2,” the former moving back and forth from sparse rattle to deftly-handled tension and loft-jazz energy. Considering the three drummers and multiple bassists, the music has a surprising amount of openness. Bass Is encompasses a range of moods and textures, and shouldn’t slip through the cracks.