Keith Jarrett’s so-called American Quartet of the 1970s was a true shapeshifter, adept at tightly reined-in pop-jazz hybrids, freeform ritualistic soundscapes and everything in between. The same went for the trio that preceded it — an early showing for the hall-of-fame rhythm team of bassist Charlie Haden and drummer Paul Motian — heard at peak strength on this fascinating 1972 live set. Anyone who knows Jarrett mainly for his famed solo piano work might be shocked to hear him picking up soprano saxophone here, as on the scampering, exuberant and ultimately explosive free-jazz ramble “Piece for Ornette,” or contributing placid flute to the lengthy soundscape that opens “Everything That Lives Laments.” At the keys, meanwhile, he’s typically brilliant, especially on the rollicking gospel-fusion groove vehicle “Take Me Back” and “Rainbow,” a tender waltz written by his then-wife, Margot. On Haden’s “Song for Che,” he moves from percussion to soprano to piano, as the trio brings the piece from a fervent abstract boil to a stirring melodic climax.