Jazz fusion (also known as fusion) is a music genre that developed in the late 1960s when musicians combined jazz harmony and improvisation with cool jazz, rock music, bebop, blues rock, modal jazz and rhythm and blues. Electric guitars, amplifiers, and keyboards that were popular in rock and roll started to be used by all best 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. These arrangements, whether simple or complex, typically include improvised sections that can vary in length, much like in other forms of jazz.