Portastatic is the brainchild of Superchunk singer Mac McCaughan, who creates its ambling, introspective albums virtually by himself. And like other "bands" with similar one-man arrangements (Palace, et al), Portastatic's three albums vary wildly based on the mastermind's moods. And while Portastatic's debut, I Hope Your Heart Is Not Brittle, was a creepy, low-fidelity shambles, The Nature of Sap's production is fuller, busier and more electronically enhanced, with lots of subtle effects and interludes. But while the first few tracks sound like Superchunk songs stripped down and slowed considerably, most of the album's remainder is bogged down with forgettable instrumentals ("Jonathan's Organ") and thinly arranged filler ("Before You Sailed Around The World," "Impolite Cheers"). McCaughan's music is almost always intriguing, but this is one of his least inspired creations.