The Song of the Earth and Dances at a Gathering show the Brit Kenneth Macmillan and the American Jerome Robbins to be a sneakily inspired pairing. With masked protagonists, one of whom is Death, the Royal Ballet master leaned in to allegory and German Expressionism. By contrast, New York City Ballet’s returned prodigal took a realist turn, with a frolicsome dance of chance encounters that nods to free love. But both hour-long ballets reflect their era. Made in the 1960s, middle and late, both are taken up with cycles of experience, journeys of discovery—well-worn tropes by now. What saves them from cliché is the choreography’s poetic plainness and music that has survived its own revolutionary aspirations: the haunting Mahler song cycle from which the Macmillan takes its name and, for Robbins, Chopin’s mercurial piano pieces. —Apollinaire Scherr