One of classical music’s great mysteries is why Schubert never finished his eighth symphony—he lived six more years after he stopped working on it. But there’s no mystery in why it has become so popular: it’s gorgeous, and it includes one of the most famous melodies ever written. Like Schubert, Gustav Mahler was a master songwriter, and he set many poems by Friedrich Rückert to music. Sasha Cooke, a “luminous standout” (The New York Times) with “equal parts poise, radiance, and elegant directness” (Opera News), sings Mahler’s Rückert Lieder with the Festival Orchestra.