Each of the three women who make up the power-sneer rock band Younger are veterans of Iowa City’s music scene. Their brand of nineties worship brings to mind the shoulder-popping rhythms of early Sleater-Kinney, while their dedication to three-part harmonies evokes the Shangri-las. Drums, bass, and guitar all grind with the swagger of musicians for whom the form is a pleasure rather than a chore.