Also known as jazz-rock fusion or simply fusion, a musical genre that merges elements of jazz with other styles of music, particularly pop, rock, folk, reggae, funk, metal, R&B, hip hop, electronic music and world music. Fusion albums, even those from the same artist, often include a variety of these musical styles.

In the late 1960s, jazz musicians began mixing the forms and improvisational techniques of jazz with the electric instruments of rock and the rhythms of soul and rhythm and blues. At the same time, some rock artists began adding jazz elements to their music. The 1970s were the most visible decade for fusion, but the style has been well represented during more recent times.

Rather than being a codified musical style, fusion can be viewed as a musical tradition or approach. 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 metres rarely seen in other Western musical forms.

In the middle 1960s, Julian 'Cannonball' Adderley began performing music that fused jazz and pop. In the late 1960s, Miles Davis (especially with albums such as Bitches Brew) and the Tony Williams Lifetime used instruments such as electric guitar, bass guitar and electric piano to create music that fused jazz with rock and other genres. Later, Herbie Hancock, Joe Zawinul, Jan Hammer and Chick Corea began incorporating synthesizers.

Jazz artists followed developments in pop music and also began using the modern recording studio's improved editing, multitrack recording and electronic effects capabilities as an adjunct to composition and improvisation. For example, Miles Davis' In a Silent Way (1969) and Bitches Brew (1970) feature extended compositions which were never actually played straight through by the musicians in the studio. Instead, musical motifs of various lengths were selected from recorded extended improvisations, and edited together into a musical whole which only exists in the recorded version. These are considered cornerstone recordings of the genre.

Many rock musicians had begun to independently approach jazz forms during the mid-1960s. The Byrds recorded in December 1965 the first version of Eight Miles High, a groundbreaking single emulating the style of John Coltrane's classic quartet. In 1966, Paul Butterfield and Mike Bloomfield recorded a long improvisational piece called East-West.

Other rock musicians also performed and recorded rock songs featuring extended improvisations and jazz-style instrumental interplay as well as longer, multipart compositions. Examples include Jimi Hendrix, the Grateful Dead, and the Allman Brothers Band in the US and King Crimson, Soft Machine, Yes and Cream in the UK. Frank Zappa released his first jazz-rock album, Hot Rats, in 1969 and continued recording fusion music occasionally during his career.

A number of prominent jazz-rock bands also had considerable success beginning in the late 1960s and early 1970s, including US bands Blood, Sweat and Tears, Chicago and Steely Dan and UK bands such as Traffic and Colosseum.

Much of 1970s fusion was done by a core of musicians who had worked with Miles Davis. In addition to Davis, important figures in early fusion were Tony Williams, Herbie Hancock, Chick Corea (with his band Return to Forever), John McLaughlin (with his band Mahavishnu Orchestra) and Joe Zawinul and Wayne Shorter with their band Weather Report.

At its inception, Weather Report was an avant-garde experimental fusion group. The band later introduced a more commercial sound, most noted in the hit song Birdland. Weather Report's albums were also later influenced by different styles of Latin and African music, offering an early world music fusion variation. Jaco Pastorius, often regarded as one of music's most innovative electric bass players, joined the group in 1976.

In the UK, the jazz fusion movement was headed by Soft Machine and If.

Chick Corea formed his band Return to Forever in 1972. The band started with Latin-influenced music (including Brazilians Flora Purim as vocalist and Airto Moreira on percussion), but was transformed in 1973 to become a jazz-rock group that took influences from both psychedelic and progressive rock. The original drummer was Lenny White, who had also played with Davis. Return to Forever's songs were distinctively melodic due to Corea's composing style and the bass playing style of Stanley Clarke, who is often regarded with Pastorius as the most influential electric bassists of the 1970s. Guitarist Al Di Meola, who started his career with Return to Forever in 1974, soon became one of the most important fusion guitarists.

John McLaughlin formed the highly-regarded fusion band the Mahavishnu Orchestra with drummer Billy Cobham, violinist Jerry Goodman, bassist Rick Laird and keyboardist Jan Hammer. The sound of Mahavishnu Orchestra was influenced by both psychedelic rock and classical Indian sounds that inspired McLaughlin. The band's first lineup split after two studio and one live albums, but McLaughlin formed another group under same name which included Jean-Luc Ponty, a jazz violinist, who also made a number of important fusion recordings under his own name as well as with Zappa,and drummer Narada Michael Walden.

McLaughlin was also an original member of drummer Tony Williams' Lifetime fusion band, which existed in several versions between 1969 and 1975 and later included Cream bassist Jack Bruce.

McLaughlin also formed a group in the early 1970s with Latin-rock guitarist Carlos Santana. Santana's San Francisco-based band blended Latin salsa, rock, blues and jazz, featuring Santana's clean guitar lines set against Latin instrumentation such as timbales and congas. Fusion influences can be heard in Santana's use of extended improvised solos on some of the group's 1970s recordings.

Other influential musicians that emerged from the fusion movement during the 1970s include guitarists Larry Coryell and Pat Metheny.

In the early 1980s, much of the original fusion genre was subsumed into other branches of jazz and rock, especially smooth jazz and jazz-pop, as the merging of jazz and pop/rock music took a more commercial direction in the form of compositions with a softer sound palette that could fit comfortably in a soft rock radio playlist. Such genres rarely contain the improvisational qualities that originally surfaced in jazz decades earlier, deferring to a more commercially viable sound more widely enabled for commercial radio airplay in the USA.

Some artists such as Davis, Corea and Zawinul continued to perform fusion music during the 1980s. Guitarist Bill Frisell has also made fusion recordings over the past two decades, along with drummer Jack DeJohnette and saxophonist Bill Evans.