Twenty years ago, Joe Westerlund moved to North Carolina with DeYarmond Edison, the pre-Bon Iver project with Justin Vernon that evolved into Megafaun. Then he became one of the region’s most prized drummers, playing with prominent acts like Mount Moriah, Jake Xerxes Fussell, and Sylvan Esso. But while he was dissolving his creeping, cellular sense of time in song-forward ensembles, there was an experimental composer waiting to come out. The first rip in the chrysalis set loose Grandma Sparrow, a capering performance-art alter ego that fused shades of Syd Barrett and Frank Zappa in psychedelic children’s music. Audacious and eccentric, it was an id explosion that served to propel Westerlund downstage, clearing the decks for a more grounded…