Jazz fusion

Fusion or, more specifically, jazz fusion or jazz rock, is a musical genre that developed in the late 1960s from a mixture of elements of jazz such as its focus on improvisation with the rhythms and grooves of funk and R&B and the beats and heavily amplified electric instruments and electronic effects of rock. While the term "jazz rock" is often used as a synonym for "jazz fusion", it also refers to the music performed by late 1960s and 1970s-era rock bands when they added jazz elements to their music such as free-form improvisation.

After a decade of development during the 1970s, fusion split into different branches in the 1980s. While some 1980s performers continued the improvisatory and experimental approaches of the 1970s, others moved towards a lighter, more pop-infused easy-listening style called smooth jazz which often included vocals. Since the 1990s, some fusion bands have also incorporated electronica, hip hop, and heavy metal.[citation needed]

Fusion albums, even those that are made by the same group or artist, may include a variety of styles. Rather than being a codified musical style, fusion can be viewed as a musical tradition or approach. Some progressive rock music is also labeled as fusion.[1] Fusion music is typically instrumental, often with complex time signatures, metres, rhythmic patterns, and extended track lengths, featuring lengthy improvisations. Many prominent fusion musicians are recognized as having a high level of virtuosity, combined with complex compositions and musical improvisation in complex or mixed metres.

Source : http://en.wikipedia.org/wiki/Jazz_fusion