With Boxer, the National have reached four albums into their increasingly lauded career, never hurrying the tempo, never over-reaching in volume or instrumental density. Instead, the quintet’s balanced on a pin, emotionally austere, if not utterly downhearted, finding brilliantly dusky ways for Matt Berninger’s lovelorn voice to mesh with a pair of unobtrusive guitars and, here, an occasional phalanx of piano, horns, and strings. The tunes roll off slowly, Berninger’s lyrics hugging the instruments with a sad brawn, rough-hewn as the drums and bass toy with angularity (try “Mistaken for Strangers,” for one) but end up woven by that voice. Drummer Bryan Devendorf presses the songs forward repeatedly, as on “Start a War,” where he gently thumps the time as the acoustic guitars frame and dot the melody, coalescing as the drums starkly chisel the melody. Nary a distortion pedal is harmed on Boxer, giving the National a magnetism so forlorn that you can’t stop listening.