San Francisco’s Mates of State — known to their parents as the married couple Kori and Jason Hammel — work at an indie-rock formula that has gotten more exercise than you’d think in recent years: two classic-pop-bent lovers banging around in the garage all by themselves. But unlike Quasi, who use the lessons they learned from their failed marriage as a cheat sheet for their corrosive relationship studies, and the White Stripes, who swear they’re brother and sister, the Hammels seem to have gotten into music only as an excuse to drive long distances from show to show in a small vehicle with just each other for company. The giddy rush that suffuses that type of young love is palpable throughout Our Constant Concern, their second full-length and their first for Illinois indie Polyvinyl. But it’s voiced through a set-up that is Quasi’s in reverse: Kori smacks her vintage organ with both hands and Jason bats at his trap set while they tangle their voices in slippery, deceptively complicated harmonies, giving melodic heft to observations like "A stolid jest takes its time on the best." Not rocket science, perhaps, but not quite simple puppy-love poesy, either.