Jon Hassell was an American trumpet player and composer. He was best known for developing the concept of "Fourth World" music, which describes a "unified primitive/futurist sound" combining elements of various world ethnic traditions with modern electronic techniques. The concept was first articulated on Fourth World, Vol. 1: Possible Musics, his 1980 collaboration with Brian Eno.

Fourth World, Vol. 1: Possible Musics is an album by Jon Hassell and Brian Eno. It was recorded at Celestial Sounds in New York City and released in 1980 by Editions EG, an imprint label of E.G. Records. "Fourth world music" is a musical aesthetic described by Hassell as "a unified primitive/futuristic sound combining features of world ethnic styles with advanced electronic techniques." The album received praise from many critics.