For the first time, electronic instruments such as the Hammond and Theramin were introduced in the post-World War II period. These instruments were at first modeled after traditional western sounds, such as that of the pipe organ, but eventually developed monophonic and polyphonic timbres of their own. The first analog synthesizer was released in the early 1950s, which gave an artist control over his music. These electronic instruments were used to create ambient soundscapes that had notes complexly layered on top of one another.
The modernist movement sought to deal with the horrors of World War II by removing conventions from their artistic style as a way of challenging the old order. One popular form of this was 12 tone music, made popular by Iannis Xenakis and Stravinsky. This music used all of the notes in a musical scale, rather than the traditional Western scale which only used a few. The result was complex music that was in many ways informed by mathematical equation.
Jazz saw a major change in the years after World War II. Big bands, or bands that featured 10 or more musicians and instruments, were on the decline, and Bebop rose in its place. Bebop music used smaller groups, usually four or five members, and placed an emphasis on solo performance. They also allowed for more advanced melodies with multiple layers and syncopated rhythms, which made the music harder to dance to, but also more complex in nature.
Another form of music that saw its start after World War II was Rhythm and Blues. This movement started when African American performers such as Little Richard and Chuck Berry began incorporating electrically powered instruments, such as the new electric guitar, into traditional blues style. These performers were soon joined by white artists such as Elvis Presley and Buddy Holly, who emulated their style and served as a precursor to rock 'n' roll music.