An articulate composer with a voracious curiosity, Nico Muhly worked for Philip Glass, wrote for the Boston Pops, and premièred a group of works at Carnegie Hall—all before turning 27. That might not be notable if not for the classical context, but it's worth keeping in mind while mulling the many ways in which Muhly resists being classed as merely "classical." His second album, Mothertongue, is all about wild digression, with subjects ranging from random blurts of mental detritus to recitations of bizarre 17th-century texts, and its sound proves ambitious yet homespun. The title composition features hiccupy singings of old data memories (addresses, names of states) over piano and strings, before "Wonders" shoves toward the exotic past with snatches of old adventure tales sung over a musical backdrop of celeste and horns that wouldn't sound out of place on an album by Björk. (Muhly has worked with her.) The last piece, "The Only Tune," enlists ghostly folksinger Sam Amidon in an ambitious distillation of an old folk song about playing a dead body like a fiddle. Like everything on Mothertongue, it's searching, quizzical, and filled with alternately fleeting and sustained passages of astonishing beauty.