George Balanchine’s Midsummer Night’s Dream begins with four suspenseful, spectral chords: a short ascending ladder that signals our arrival to a different world. The curtain rises, and we’re greeted by a single fairy-child, about to pose, one assumes, the centuries-old query: How now, spirit? Whither wander you? Set to Mendelssohn’s Midsummer overture and incidental music (and a few other of his compositions), Balanchine’s ballet is performed regularly by New York City Ballet.