Samuel Barber’s Knoxville: Summer of 1915 is the centerpiece of Walking in the Dark, American soprano Julia Bullock’s debut solo album. Her impassioned interpretation plumbs the mix of comforting nostalgia and existential longing Barber writes into the music. Bullock’s couplings are fascinatingly varied. Her version of “Brown Baby,” recorded by Nina Simone and others, has both tenderness and a roiling sense of outrage, while the Connie Converse song “One by One” distills a rare combination of poise and poignancy. The gospel-tinged “I Wish I Knew How It Would Feel to Be Free” highlights Bullock’s acute response to words, and her rapt account of Sandy Denny’s “Who Knows Where the Time Goes” brings the album to a breathtaking conclusion.