When you play in a band (presumably) named after an early nineteenth-century Russian uprising, fronted by a dude from Oregon who writes magical YA novels, and that is often the recipient of positive album reviews that make liberal use of the words “shanty” and “accordion,” the last thing anyone expects out of you is any semblance of rock-and-roll swagger. Well, on their new track, “Down by the River,” the lead single from January’s just-announced The King Is Dead, the Decemberists still sound like precise, hyperliterate (shout out to gabardine!) folk-rockers. But, in a trend begun on 2009’s The Hazards of Love, there’s an appreciated extra layer of oomph and grit to the proceeding. Maybe it’s the squealing young-Springsteen harmonica, or Colin Meloy sounding more pissed off than bereaved, or the beefy guest assists from Peter Buck and Gillian Welch, but “River” almost has us convinced the Decemberists could one day, theoretically, incite, and then subsequently win, a street brawl.