Question: The Unanswered Question is a ballet made from work by a man who was regarded as what?
Sentence (from "Charles Ives"): He combined the American popular and church-music traditions of his youth with European art music, and was among the first composers to engage in a systematic program of experimental music, with musical techniques including polytonality, polyrhythm, tone clusters, aleatory elements, and quarter tones, foreshadowing many musical innovations of the 20th century.
Relevant evidence: No