On her striking debut EP, Promises, bicoastal synth-pop upstart Ryn Weaver makes a very strong first impression. With the sonic backing of Charli XCX, Benny Blanco, Cashmere Cat, and Passion Pit mastermind Michael Angelakos—who all contributed their songwriting services and production acumen to the glittering single “OctaHate”—Weaver exhibits remarkable vocal confidence. She turns the finely sliced, xx-like guitar minimalism at the heart of “Sail On” into a maximalist heart-thumper, while the EP’s deeply melodic title cut finds her braiding together ribbons of her own vocals with equal aplomb.