Hart's musical activities outside the Dead have been extensive. In 1976, the Dead's Round Records label released Diga by the Diga Rhythm Band, an early experiment in worldbeat fusion put together by Hart. His interaction with drummers from around the world sparked an abiding interest in the role of the drum in other cultures -- and a steadily expanding curiosity about non-Western musics. 1979 and 1980 saw the release of two albums of music from the film Apocalypse Now, much of it contributed by Hart. In 1983, Hart released albums under the heading The World. These began with a reissue of Diga Rhythm Band (an album by Babatunde Olatunji produced by Hart). Then came a series of albums of music Hart had recorded around the world. In 1989 Hart released Music to Be Born By, an album based on the heartbeat of his son in the womb, and 1990 saw the simultaneous release of Hart's first book, Drumming at the Edge of Magic, and an album, At the Edge. In 1991, another book and disc, both called Planet Drum, appeared. Both albums made the upper reaches of the new age and world-music charts. Supralingua followed in 1998.