Listening to Radiosonde's sophomore album (its first, Sanctuary, was released in 2009 on Starnet Muzik), one quickly begins to appreciate why the group chose to use cloud names (“Cirrus”) and nature-related imagery (“Equinox,” “Troposphere,” “Monsoon”) for so many of the recording's song titles, as there's an attempt to distill into aural form the experience of taking in the panoramic landscape from the height of a drifting weather balloon. Not surprisingly, then, one encounters an expansiveness in the largely guitar-generated (electric and acoustic) improvisations the Japanese duo of Hayati Aoki and Takashi Tsuda create under the Radiosonde name (which itself means “weather balloon”); their music is anything but one-dimensional, however, as it's fleshed out by the sounds of chroma harp and, on this recording, by the contributions of Sawako to three of its eleven pieces, and though it might be rooted in improvisation, it's hardly bereft of melody either, as the plaintive closer “April” makes clear, for example.A dreamy quality pervades tracks such as “Blue Flag on the Hill,” whose delicate, pastoral lilt grows ever more hypnotic over the course of its eight minutes, while “Equinox” registers as an especially lovely folk setting of acoustic guitar picking. The chroma harp also plays a significant role in the group's shimmering sound, with its sparkling strums a natural complement to the tremolo shadings of the electric guitar during “Troposphere.” Sawako contributes field recording materials to the background of “Windcoming,” and her voice lends “Cirrus” a distinguishing character, even though the vocals largely merge with the crystalline guitar sounds to form a gauzy cloud-like mass. That crystalline design is taken to an even more grandiose level when “Cumulonibus” billows radiantly for five entrancing minutes. There's a sense in which the album's material, being by design so restrained and soothing, could be seen as lacking in presence or dynamism. But criticizing it for being so would misjudge the group's intentions and the album's deliberately ambient-styled character. Radiosonde should instead be assessed on its own terms as a purposefuly meditative and pastoral collection of guitar-based moodscaping.