Cusk is a London-based band led by Esmé Creed-Miles and Evie Hilyer-Ziegler. They’ve spent the past couple years building a fan base in their home area, almost entirely through live performances as they’ve taken on increasingly high-profile support gigs. This week, they released their debut single, “Blu Tac Piano,” and it’s a stealthy stunner. Slow and emotive, the song carries an aching power. It builds to a marvelously messy coda that invites comparison to PJ Harvey circa the angular, confrontational come-ons of To Bring You My Love. I’ll type the word again: stunner.