Harris claimed to have begun his music education by listening to his parents, especially the mother, sing folksongs while accompanying themselves on the guitar. Laura also taught him piano on an instrument her husband had bought for her (he recalled taking lessons from Jode Anderson as well), the youngster eventually learning to read some of the Mozart sonatas and other works of the standard repertoire. He took his first steps toward creativity during this period when he began picking out harmonies on the instrument. Harris later studied organ with Charles Demorest and Ernest Douglas and took up the clarinet with Harry Baldwin, playing the latter instrument in the Covina High School orchestra. A figure he remembered as being especially important to him during this period was Alec Anderson, a local organist around whom a club of intellectually- and culturally-inclined young people formed. It was Anderson who took Harris to his first symphony concert and contributed to the broadening of his musical culture by playing recordings of some of the major Classical artists of the period (e.g., Caruso, McCormack, Kreisler, and Paderewski). (The composer later repaid this debt by employing Anderson, who was to fall on hard times, as his secretary during the early40s.)Harris was quite athletic as a youth, taking up football (in which he broke his nose, an arm, and some fingers), tennis, and baseball. He later claimed to have become so proficient in the lastnamed that he was offered a contract with the Chicago Cubs (who trained summers on Santa Catalina Island), which he turned down, believing he was not sufficiently accomplished to play at that level.
Among the things that affected the future composer profoundly as a youth and later found resonance in his music were the isolation and loneliness of the sparsely populated rural surroundings in which he lived; the sounds of nature, especially birdsong; the whistles of the Southern Pacific and Santa Fe railroads echoing from opposite sides of the Valley; and, of course, his parents* folksinging, of which Elmer's whistling of When Johnny Comes Marching Home, "with jaunty bravado as we went to work on the farm in the morning and with sad pensiveness as we returned at dusk" (from the preface to published score) planted in young Harris the "unconscious realization" of the dual nature of the tune that was later to serve almost as a kind of "theme song" for him.