Some musicians wait until just the right moment in a song to let loose with their telltale big wail, or to rip into a fiery guitar solo. With Andrew Bird, it's all about the whistling. In "Masterswarm," the second song on his fine new Noble Beast, Bird starts slow, moaning over some simple guitar-plucking before adding light Latin electro-beats and delicate, feathery violin—softly folding Nick Drake into Caetano Veloso. Then Bird breaks out his signature whistle, which hovers high and lonesome above the fray, like the last gasp of the human spirit. "Masterswarm" is about the exciting, terrifying process of transforming, as delineated in lines like, "Inside me grows a man who speaks with perfect diction / As he orders my eviction / As he acts with more conviction than I." By the end of the song, electronic percussion takes over, drowning out the rough grunts of the beginning. But before Bird disappears, he gives a little whistle. Naturally.

The downside to having a winning formula like Bird's is that he can put all the pieces in place and come away with something pleasant and workable without having to push further. About a third of Noble Beast coasts along like this, generating an amiable atmosphere while advancing the album's contemplations of evolution and the loss of self. But then Bird arrives at a song like "Fitz And The Dizzyspells" (which pumps up the western-ballad form with a dose of '60s go-go), or "Anonanimal" (which turns every stringed instrument at hand into the gears of some magnificent rhythm-generating machine), and suddenly Noble Beast turns into a higher form of pop music, so beautifully, horrifyingly evolved.