The program highlighted the impressive gifts of the soprano Julia Bullock — a mesmerizing performer who combines an alluring voice with a natural theatricality. During recitals, singers often stand uneasily onstage, their movements appearing calculated. But Ms. Bullock imbued every song with myriad physical nuances that seemed natural and spontaneous; subtly unclenching a fist, arching her eyebrows, pointing a finger, or narrowing her gaze.