It was during this period that Harris also undertook his most intensive investigation into the history and resources of Western Music, with special concentration on the literatures of the high Renaissance and Anglo-Celtic folk music, an effort that was to bear potent fruit in the development of his own idiom. Some striking and original creations emerged during the 20s and 30s, when the joy of making music was fresh and high and family pressures at a minimum, among them the Concerto for Piano, Clarinet, and String Quartet; the Sonata for Piano; the Concerto for String Sextet; Symphony for Voices; Quintet for Piano and Strings; Soliloquy and Dance; Symphony 1933; and Symphony No. 3. Some of these have proven to be among his strongest and most durable scores.
Harris's second period lasted from the late30s through the late40s. It was in these years that he achieved the greatest refinement of his harmonic style (with simple triads predominating in some works) in tandem with the maturation of a melodic idiom capable of conveying a strong and direct surface communication while possessing great subtleties of tonal nuance and phrase construction.
The 1940s also initiated his deepest involvement in what might be termed musical Populism, as exemplified in various compositions for patriotic occasions, numerous arrangements and symphonic treatments of folk materials, and the creation of music for amateurs and school-age performers.
A new dimension was added to Harris's instrumental palette during this period, the result of his involvement with the sonorities of the symphonic and military bands and his resulting contributions to the foundations of an indigenous literature for the wind medium. These experiences also influenced his writing for orchestra.
Possibly due at least in part to the diverse compositional challenges he undertook during the 1940s, some of his most polished work dates from this decade: a maturing and increasingly flexible technique is revealed in several a cappella chorale pieces, the American Ballads for piano, chamber compositions like the Sonata for Violin and Piano, and such representatives of the larger media as the Symphonies Nos. 5 and 6, Concerto for Two Pianos and Orchestra, Kentucky Spring, and Cimarron.
