Hey, Terrible Buttons freaks: you’ve heard Mama Doll, right? If you haven’t, here’s the deal: Sarah Berentson — the tiny singer and keyboard player in the Buttons with the big, old voice — has started this side project with Austin Case and Jen Landis. Together, the three women form a sound that is beautiful while being bare and primal in a feminine sort of way. The band’s music is simple, with only ukulele strumming and maybe the beat of a simple floor tom. Mama Doll is all about the way these women harmonize, and about the things they say. Yes, it’s pretty. But Mama Doll is also sort of dark and haunting, so if you’re a Buttons fan, you’re going to love this band.