The compositional style that includes atonality, bitonality, and polytonality is associated with which time period?

The compositional style that encompasses atonality, bitonality, and polytonality is primarily associated with the 20th and 21st centuries. This period is characterized by a significant departure from the traditional tonal structures that dominated earlier music. Atonality refers to music that lacks a tonal center, meaning it does not emphasize a specific key or home note; bitonality involves the simultaneous use of two different keys, while polytonality employs multiple keys at once.

These innovative techniques reflect the exploration and experimentation prevalent in modern music, as composers sought to expand the boundaries of what was considered music. The emergence of styles such as twelve-tone music by Arnold Schoenberg and various avant-garde movements showcases how composers from this period embraced complexity and dissonance. In contrast, the other periods—Classical, Romantic, and Baroque—were defined by more structured harmonic languages and tonal clarity, which do not align with these modern concepts.