As a jazz concerto, "Rhapsody in Blue" is written for solo piano with orchestra. A rhapsody differs from a concerto in that it features one extended movement instead of separate movements. Rhapsodies often incorporate passages of an improvisatory nature—although written out in a score—and are irregular in form, with heightened contrasts and emotional exuberance. The music ranges from intensely rhythmic piano solos to slow, broad, and richly orchestrated sections. Consequently, the "Rhapsody" "may be looked upon as a fantasia, with no strict fidelity to form."