Aaron Copland's Piano Sonata comes chronologically from the very heart of his "vernacular" period, but bears little stylistic resemblance to the works around it. The opening sketches date from June 1939, just after Copland had completed the incidental music he would later fashion into the tone poem Quiet City. In December 1940, Copland was named by Nelson Rockefeller to an advisory panel within the State Department's Office of Inter-American affairs. Copland spent most of 1941 touring South America as part of the Roosevelt administration's Good Neighbor policy, getting to know South American music and composers, giving master classes, and concertizing. In Santiago, Chile, in September, Copland put the finishing touches on the Piano Sonata, premiering it himself in Buenos Aires on October 21, 1941.
Copland once noted that "a piano work, in my case, (is written) when I am stuck with ideas that have nowhere else to go." Copland studied sonata form extensively with Rubin Goldmark in Cleveland as a youth, and sticks to standard sonata-allegro form very definitely in this sonata, varying the opening Molto Moderato with appropriate contrast and periods of roughly equal length. The Scherzo vivace alternates abrupt, jazz-derived ideas with a slower, more relaxed trio section. The final Andante sostenuto departs from standard sonata form, in that it takes its basic working material from the second movement Trio and consists of static chords, giving an impression of immobility, like a clock winding down.
Copland had relatively little to say about the Piano Sonata, although he was in general somewhat tight-lipped about his work, preferring to let the music speak for itself. However the sonata is rarely discussed in the context of Copland's music, and is as seldom heard in concert, in spite of its historical placement among the most popular of his works. Indeed, the Piano Sonata inhabits both of Copland's main spheres of activity to that time, taking the spindly, naked forms of his vernacular music and combining them with the tougher language of his early Piano Variations (1930). Nonetheless, the Piano Sonata is one of his finest creations in terms of its concentration of expression, variety of mood, and its finely tuned balance of both seriousness and dry wit. One important early advocate of the Copland Piano Sonata was Leonard Bernstein, who played it expertly early in his career and made a fine recording of it for RCA Victor in 1947.