This album is the result of two remarkable men—the physicist Donald (“Don”) Gurnett, and pioneering composer Terry Riley—brought together by David Harrington, founder and first violinist of the Kronos Quartet. In the early 1960s, Don Garnett developed instruments to record sounds encountered by spacecraft beyond the Earth’s atmosphere. The Voyager 1 and 2 spacecraft, launched in 1977, were provided with some of Garnett’s equipment. The recordings they obtained proved that, contrary to popular perception, even outer space is not a vacuum, but has a density through which soundwaves can be carried. Furthermore, some of those sounds appeared “musical.” In 2000, Bert Ulrich, then curator of the NASA Art Program, invited the Kronos Quartet to make use of those sounds as recorded on the Voyager expeditions. Harrington immediately recruited Terry Riley, who enthusiastically embraced the project. This album is the result, involving not only the Kronos Quartet and the recordings, but also a choir which makes a serene appearance in “Earth Whistlers.” Riley complements these sounds from space with his usual reassuring blend of folk and world music-inspired style, perhaps most attractively in “Planet Elf Sindoori.” After all, the perception of these sounds as being “musical” is ultimately our human perspective. The Kronos Quartet embrace Riley’s humane qualities, bringing warmth to these literally un-Earthly sounds.