Jazz fusion is a musical fusion 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 expanded the improvisatory and experimental approaches through the 1980s and 1990s.
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. 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. According to bassist/singer Randy Jackson, jazz fusion is an exceedingly difficult genre to play. According to Jackson, " I [...] picked jazz fusion because I was trying to become the ultimate technical musician-able to play anything. Jazz fusion to me is the hardest music to play. You have to be so proficient on your instrument. You have been playing five tempos at the same time, for instance. I wanted to try the toughest music because I knew if I could do that, I could do anything."