Which style of jazz is characterized by fast tempos and complex chord changes?

The style of jazz that is characterized by fast tempos and complex chord changes is Bebop. Emerging in the 1940s, Bebop marked a departure from the dance-oriented rhythms of earlier jazz forms like swing. It focuses on intricate melodies and harmonies, featuring rapid tempo and a high degree of improvisation. Musicians in this genre, such as Charlie Parker and Dizzy Gillespie, often employed advanced chord progressions, which required a greater technical proficiency and understanding of music theory than many of their predecessors.

Bebop's emphasis on personal expression and innovative soloing also contrasts with the structured arrangements found in other styles. This genre not only changed the way jazz was played but also influenced the direction of music as a whole, paving the way for future genres and ensuring its place in jazz history as a prominent and complex art form.