Jen Shyu, the Illinois-born cross-genre vocalist of East Timorese and Taiwanese descent, recently made a formidable contribution to saxophonist Steve Coleman's latest album, The Mancy of Sound. That was a group exercise, but Shyu (who has worked with Coleman for eight years and in her Jade Tongue band with New York saxist David Binney for three) makes much more intimate music here – in a duo with former Anthony Braxton bassist Mark Dresser. Shyu is a remarkable phenomenon, shifting registers with startling ease and tonal resourcefulness, moving from conventional pitching to a yodel-like ambiguity without fuss. She blends fragile, light sounds with dark, low notes, ruminative hummings and improv in a personal language that fuses English, Taiwanese, Mandarin and several others. Dresser, who is a precise, resoundingly emphatic bassist with a composer's sense of shape, provides low-end contrasts to his partner's vaporous musings – sometimes stalking her movements, sometimes furnishing driving basslines, jazzy fast walks or fiercely abstract bowings like the work of the UK's Barry Guy. Steve Coleman listeners who have become admirers of Shyu may be fascinated by these uncompromising virtuoso dialogues, as might any student of contemporary improv-vocal technique. But it's a demanding trip for the unprepared.