In June 1913, a sixteen-year-old Californian with no formal musical training wrote a solo piano piece, "Adventures in Harmony", employing "primitive tone clusters." Henry Cowell would soon emerge as the seminal figure in promoting the cluster harmonic technique. Ornstein abandoned the concert stage in the early 1920s and, anyway, clusters had served him as practical harmonic devices, not as part of a larger theoretical mission. In the case of Ives, clusters comprised a relatively small part of his compositional output, much of which went unheard for years. For the intellectually ambitious Cowell—who heard Ornstein perform in New York in 1916—clusters were crucial to the future of music. He set out to explore their "overall, cumulative, and often programmatic effects."