In 1959, literary critic Warren Tallman published a landmark study of Kerouac’s spontaneous method that focused on The Subterraneans, a novel Kerouac wrote over the course of just three days in 1953. This chapter builds on Tallman’s work (and other subsequent scholarship) to show how Kerouac adopted the use of spontaneity from what he understood to be a jazz aesthetic, purposively repudiating the reigning New Critical norms that dictated “good” fiction must exhibit certain kinds of “unity” and “selectivity” of expression. This chapter therefore takes The Subterraneans as a concentrated case study in how Kerouac composes, rehearses and constructs a Spontaneous Prose text.