 While swing music tended to feature orchestrated big band arrangements, bebop music highlighted improvisation.Typically, a theme (a "head," often the main melody of a pop or jazz standard of the swing era) would be presented together at the beginning and the end of each piece, with improvisational solos based on the chords of the tune.Thus, the majority of a song in bebop style would be improvisation, the only threads holding the work together being the underlying harmonies played by the rhythm section.