American composer and bassist Christopher Roberts has spent much of his career outside the United States, studying either non-Western musical traditions (he is a master of the qin, a Chinese stringed instrument) or "the natural prosody of music." In the latter case, he spent time in the jungles of Papua New Guinea, living in villages and absorbing indigenous traditions as well as the profligate natural sounds that surrounded him. The five pieces collected here, for three string basses, are reflections of his experience in the jungle. Roberts' most obvious musical influence is the throbbing pulse of early minimalism, but his music is so rich in its textures and gestures and harmonies that his voice is distinctive. As a bassist, he understands how to draw such a prodigious variety of sounds from the instrument that the lack of higher voices never seems like an impediment. Each piece has its unique character; some are almost traditionally contrapuntal, but a primal energy, with its own mysterious, visceral logic, animates most of Roberts' work. Two of the most immediately engaging pieces, Hornbills and Flying, were inspired by the sounds of the large birds in flight. The first is fast and the second slow, but they both convincingly convey a sense of weightless soaring, which is quite an achievement using only instruments as weighty as basses. Composer Mark Morton and James Bergman deliver virtuosic performances that capture the diverse moods of the music, from delicate to frighteningly feral. The sound is clean, with a nicely resonant ambience that lets the listener feel the deep vibrations the basses produce.