Begun on a train from Svendborg in Denmark to Prague in 1937 and developed until his forced departure from the United States in 1948, Hanns Eisler’s Reisesonate (Travel Sonata) is inextricably linked with the composer’s displacements. This article positions the Reisesonate in several contexts—its material, performance, stylistic, and political histories—that challenge the directional simplicity of emigration as the move from home to exile, from nation to nationless-ness. We situate the sonata’s genesis against the background of Eisler’s travels and discuss strategies in Eisler scholarship vis-à-vis his places. Mobility emerges in an analytical reading of the work that destabilizes static notions of musical modernism. Performance history and further documentary evidence, including the surveillance files of the British Security Service, provide portraits of the composer on the move. We suggest that the Reisesonate provides musical counterpoint to Eisler’s biography, like a travel companion, and sheds light on the journeying that defined his life at mid-century.