On "Minamo" the violinist Carla Kihlstedt and the pianist Satoko Fujii ply the craft of post-jazz musicians all over the world: live, free-improvisation duets. Most records like this imply that the two musicians rarely get a chance to play together. (If they did, they might invest in the partnership more: write some music, book a studio, set up a Web site for the project, give it a name.) And some are perfunctory, of course. But not this one. "Minamo" is extraordinary, a series of tight, dramatic events.

Both Ms. Kihlstedt, who lives in California, and Ms. Fujii, who lives in Japan, have conservatory backgrounds. Both eventually threw themselves into non-genre-specific writing and improvising, drawing on rock, Cecil Taylor, Bartok and much else; you're more likely to find them in a jazz festival than any other kind. (Ms. Kihlstedt is a member of the bands Sleepytime Gorilla Museum and 2 Foot Yard; Ms. Fujii leads her own trio, quartet and orchestra.) They performed together onstage in 2002 and 2005, in San Francisco and in Wels, Austria, and this disc captures both concerts.

Even without written music the musicians have plenty of ground under their feet: vamps, patterns, echoed motions. Both play with virtuosic precision and a great range of technique, even when the music becomes gestural and built on hummingbird pulses, glassy wipes of the violin strings, dark rumbles of rubbed piano strings. The whole record, but especially the second concert, runs on its own vivid tension.