The avant-garde (or “free jazz”) musicians who came to the forefront of jazz during the late 1950s and early 1960s mounted a revolutionary movement that challenged all the conventions of the idiom, aligning their innovations with the progressive social and political changes of the era. This chapter looks at the leading exponents of the music, including Ornette Coleman, Cecil Taylor, and Albert Ayler. But just when jazz seemed ready to sever completely its relationship with a mainstream audience, a new movement known as fusion (or jazz-rock fusion) attempted to broaden the music’s appeal by drawing on the new sounds of electrified commercial styles. Miles Davis, previously seen as an advocate of bebop, cool jazz, and other jazz movements, emerged as the leader of this new approach, signaled by the release of his hit album Bitches Brew. In the 1970s, a different kind of fusion style emerged, associated with the ECM record label in Germany, which combined jazz with ingredients drawn from classical music, world music, and other sources. This chapter traces the history of these contrasting styles and their major exponents, including Keith Jarrett, Pat Metheny, Chick Corea, Herbie Hancock, and the band Weather Report