Saxophonist David Liebman and pianist Marc Copland co-led a quartet with bassist Mike McGuirk and drummer Tony Martucci on last year's Lunar. Now they return to hatOLOGY as a duo, developing their impressive rapport over the course of two discs - the first in-studio, the second live, both recorded on the same date.

Liebman has done some of his most remarkable work in a piano-horn duo setting, most notably with Richie Beirach, his partner in the bands Lookout Farm and Quest. Copland, undaunted by this historical baggage, ably fashions a unique space for himself alongside Liebman's preternaturally powerful tenor and soprano saxes.

As on Lunar, the sets consist of standards as well as originals by both players. Copland's entries, "Bookends" and "Blackboard," are lyrical and tempo-based; the former appears in two takes, placed at the beginning and end of the studio program. Liebman's tunes, in contrast, tend toward the spacious and abstract. First we hear the dark rubato cadences of "The Searcher," and later the dissonant counterpoint and soprano squeals of "Nadir."

The only standard on disc one to feature the duo is "In Your Own Sweet Way." Elsewhere, Liebman takes an unaccompanied tenor turn on "Lester Leaps In," and Copland reciprocates with "When You're Smiling." Is it a coincidence that the two tracks begin with nearly the same melodic figure, in the same key?

Jimmy Giuffre's "Cry, Want," which the full quartet also tackled on Lunar, leads off the second duo disc. This evocative dirge in E minor first appeared on Giuffre's Fusion, a 1961 Verve release that has since been reissued by ECM as part of the two-disc compilation 1961. Originally featuring Giuffre on clarinet, Paul Bley on piano, and Steve Swallow on acoustic bass, "Cry, Want" takes on a very different quality when voiced by Liebman's gruff tenor.

For much of the remainder of the live set, the duo parses three modern masterpieces. First there's a staggering, 12-minute reading of Herbie Hancock's "Maiden Voyage," then an equally exhaustive "Impressions," with Copland favoring major-key tonalities on the latter. Liebman cries to the heavens on tenor on his 9/11 remembrance "WTC" and returns to soprano for the closing "Blue In Green," which Copland peels away to the very harmonic essence.