Voices was commissioned by the Boston Symphony Orchestra and the Fromm Foundation for the 1970 Tanglewood Festival, where it was premiered under the direction of Gunther Schuller. Its score calls for a large and varied percussion section -- including wood drums, brake shoes, suspended bottles, West African Talking Drums, large West African Master Drums and African gourd rattles -- as well as amplified piano and string basses, and the traditional orchestral instruments, whose contribution is augmented by humming, whistling and moving. Although earlier material returns in later sections -- notably in the richly contrapuntal tapestry of its closing minutes -- Voices pursues an essentially continuous and linear exploration of sound. Together with its incessant polyphonic activity, and frequent shifts of dynamics, timbre and sound patterns, this generates a tensile structure in which unpredictability and change become substantial musical elements. At the same time, however, this open-formed multiplicity is rooted to an almost omnipresent foundation of sustained clusters, a propensity for sinuous lines based on involuted chromatic pitches (articulated clusters, in other words) and a familial resemblance binding its variegated musical gestures. The result is an organic synthesis of unity and diversity, continuity and contrast. The composer has noted: "Voices is a one-movement composition in which diverse kinds of musical motion, timbral combinations and spatial relationships are intrinsically combined with specific musical events to project a uniform musical idea. The works proceeds from statements of short, clearly articulated, relatively independent sections, to longer, more organically interrelated sections. The piece is based upon the development of the interrelationship of those sections. The composition is called Voices not only because members of the orchestra are asked to use their voices as well as their instruments, but also because the basic musical gestures which underlie the composition were conceived as orchestral renderings of vocal musical expressions."