Alvvays revolves around the acerbic songwriting of singer-guitarist Molly Rankin. The daughter of the late Celtic fiddler John Morris Rankin, she started finding her own footing as a teenager, blending her folk roots with a more jangly, melodic brand of modern indie-pop. The Canadian quartet—which also features keyboardist Kerri MacLellan, guitarist Alec O’Hanley and bassist Brian…