While he's experimented with larger ensembles on albums like Pomegranate (Cryptogramophone, 2001), contrabassguitarist Steuart Liebig tends to favour the more intimate context of the quartet. But his groups have been anything but conventional, with his three Quartetto Stig albums featuring violin, trumpet, contrabassguitar, and drums, and last year's Quicksilver (pfMentum) a combination of flute, violin, contrabassguitar, and percussion. Still, despite the unorthodoxy of his instrumentation, there's always been a rhythm section.

Not so on Delta, which, for Liebig, most heavily blurs the line between contemporary composition and improvisation. Featuring flautist Ellen Burr (back from Quicksilver), clarinetist Andrew Pask, and bassoonist Sara Schoenbeck, Delta has more to do with modern classical concepts than traditional jazz harmonies. Both Pask and Schoenbeck were recently seen on left coast scene progenitor Vinny Golia's Large Ensemble: 20th Anniversary Concert (Nine Winds, 2005) DVD, another release that demonstrated how the long-held line between jazz improvisers and classical interpreters exists no longer. Delta occupies a similar space, but in its smaller size avoids the chaos that sometimes characterizes Golia's large ensemble.

Delta is no easy listen, deceptive though it might be with the relatively soft tones of the flute and clarinet, and the warm low end of the contrabassguitar, bassoon, and bass clarinet. While Liebig's electric contrabassguitar would appear to be odd man out in the lineup, it feels equally organic, and meshes well with the wind instruments.

Liebig also uses prepared techniques to give his instrument a more percussive texture, as on "Dynamite's Dionysian Dance, one of the more rhythmically insistent tracks on the disc, and Secret One-Hand Shake, where his instrument is altered so much that it loses clarity, creating a clangy, almost mechanical sound beneath Pask's clarinet solo.

Liebig describes "Our Lady of the Illuminated Hand as "a requiem of sorts, and its somber mood certainly alludes to darker matters. Between dissonant harmonies, Pask's multiphonics and Liebig's gut-deep tones, there are references to 20th Century composers like Ligeti. But with its improvisational component, it also goes to unexpected places that more formal classical composers would never envisage. "Light Cloud, Dark Cloud is equally brooding, but purer of tone, even at times approaching a dark lyricism.

They may not know each other, but there's evidence that Liebig and British ex-pat multi-instrumentalist Fred Frith come from some of the same musical places. While more detailed in structure, "Seven Secrets About Time bears resemblance to some of Frith's '70s group Henry Cow's chamber-like passages on Unrest (East Side Digital, 1974) and In Praise of Learning (East Side Digital, 1975).

While Liebig has worked within conventional rhythm section frameworka on albums like trombonist Scot Ray's Active Vapor Recovery (Cryptogramophone, 2003) and percussionist Gregg Bendian's Interzone record Myriad (Atavistic, 2000), his own path is moving more towards a classically informed chamber aesthetic. Beautiful may not be a word that comes immediately to mind when describing Delta, but there is something strangely compelling about Liebig's blend of detailed structure and more open-ended improvisation, making Delta a worthwhile investigation for the open-minded listener.