Vocalist Theo Bleckmann only occasionally sings in an identifiable language, a trait that reinforces the impression that he is of another world, a messenger graced with an ethereal sense of beauty and a childlike fascination for exploring the unknown. His style is evocative and beckoning rather than infectious, and sympathetic listeners will find themselves willingly treading fresh terrain, sometimes soft like a swaddling cloth, sometimes strange, dark and subterranean.

Guitarist Ben Monder is the perfect foil for Bleckmann's sensory journeying. Employing unique chord voicings and a volume pedal, Monder delicately breathes in and out of the music, but when the feeling hits him he can also conjure a pulverizing heavy-metal tone. He doesn't so much play his instrument as paint with it -- sometimes using large blocks of color a la Rothko, sometimes with pointillist precision, and at still others he constructs looping abstractions, an aural Jackson Pollack. Monder has released three critically acclaimed jazz CDs as a leader and has also worked with the bassist Mark Johnson and legendary jazz drummer Paul Motian.

Bleckmann's 2000 CD, "Origami," features Monder as part of a larger band that includes vibraphone, electric bass and drums. Like the art form itself, "Origami" at times takes on a delicate architecture imbued with the life and spirit of the world -- in this case, a world imagined through sound. The CD includes a few unique interpretations of jazz standards, but most of the music on "Origami" is original.

Commenting by e-mail from New York on his partnership with Monder, Bleckmann says: "Our music has an unusual and very instrumental approach to the voice and runs the gamut from high-speed unisons to slow and heartfelt ballads. My approach to jazz singing is to shy away from the standard approach of the guitarist being a mere accompanist to the singer. In my performances with Ben, I love to immerse myself in a world of pure sound, merging with the guitar on the equal basis of music."

The duo's upcoming tour of Japan marks their third swing through the country and, like their last, includes a stop at the Yokohama Jazz Promenade. In addition to the performances, Bleckmann will give a seminar on voice at Tokyo BASH on May 30.

If jazz singing strikes you as music that stopped evolving after the 1950s, except for a handful of stars such as Cassandra Wilson and Bobby McFerrin, you will be pleasantly surprised by Bleckmann and Monder's forays into the musical beyond. And with musicians as deep and resourceful as these two, the duet format will likely stretch their talents and elicit a performance that would be unimaginable with a full band or, really, by anyone else.