Nmperign, a Boston group whose nucleus consists of soprano saxophonist Bhob Rainey and trumpeter Greg Kelley, is known for exploring the quiet side of free improvisation. The group usually bases its music around long tones and extended-technique effects, and its improvisations often sound a little like electronic drones. Nmperign's first record, 44'38", included Kelley and Rainey alongside percussionist Tatsuya Nakatani. 44'38" was, in many ways, a straightforward free improv album, but it featured glimpses of the signature sound that Nmperign would later develop. In 1999, Nmp...