On August 2, 1946, Arnold Schoenberg suffered a nearly fatal heart attack. Shortly afterward, almost as though in reaction, he set to work on the String Trio, Op. 45, composed between August 20 and September 23. Commissioned by Harvard University, the String Trio was partially mapped out prior to the composer's heart attack; still, Schoenberg explained to friends and students that he wrote the work with clear programmatic intent specifically related to his infirmity and recovery. The Trio is filled with extreme contrasts and what appear to be nonsequiturs. Schoenberg's onetime pupil Leonard Stein later explained that "the many juxtapositions of unlike material within the Trio [are] reflections of the delirium which the composer suffered during parts of his illness.... These unusual juxtapositions also represent...the alternate phases of 'pain and suffering' and 'peace and repose' that Schoenberg experienced." In an unpublished essay, Schoenberg provided another perspective on the work: "I began the Trio, of which I have told many people that it is a 'humorous' representation of my sickness, soon after I was over the worst." Schoenberg undoubtedly kept these comments private because of his inherent mistrust of program music.

—John Palmer