Jazz fusion (also known as jazz rock, jazz-rock fusion, or simply fusion) is a popular music genre that developed in the late 1960s when musicians combined jazz harmony and improvisation with rock music, funk, and rhythm and blues. Electric guitars and basses, amplifiers, and keyboard instruments (including electric pianos and organs) that were popular in rock began to be used by jazz musicians, particularly those who had grown up listening to rock and roll.
Jazz fusion arrangements vary in complexity. Some employ groove-based vamps fixed to a single key or a single chord with a simple, repeated melody. Others use elaborate chord progressions, unconventional time signatures, or melodies with counter-melodies, in a similar fashion to progressive rock. These arrangements, whether simple or complex, typically include improvised sections that can vary in length, much like in other forms of jazz.