Nadine Sierra stars in one of opera’s ultimate soprano roles, the sleepwalker at the heart of Bellini’s La Sonnambula, opposite tenor Xabier Anduaga as her fickle fiancé. In his first Met production, Rolando Villazón—the renowned singer who has embarked on a parallel career as a stage director—brings new vigor to Bellini’s poignant drama, probing the psyche of the opera’s heroine and the suffocating community she can escape only in her dreams.