By his 2015 solo debut, Jamie xx had not only established a signature sound but an entirely new mood—something between tingling bliss and numbing heartbreak. It's a feeling that brooding romantics quickly clung to: London Grammar's ambient dubstep captures The xx's misty allure, while FKA twigs' R&B slithers in the heat of pulsating synths and James Blake melts hearts in blurry, bassy balladry.