He subsequently worked with minimalist composers Terry Riley (on a 1968 recording of In C) and La Monte Young (as part of his Theatre of Eternal Music group), and studied under Hindustani singer Pandit Pran Nath.

He subsequently worked with musical artists such as Talking Heads, David Sylvian, Farafina, Peter Gabriel, Tears for Fears, Ani DiFranco, Techno Animal, Ry Cooder, Moritz von Oswald, and Carl Craig.

[1] Born in Memphis, Tennessee, United States,[1] Hassell received his master's degree from the Eastman School of Music in Rochester, New York.

He pursued his Ph.D. in musicology in Buffalo and performed in La Monte Young's Theatre of Eternal Music in New York City, contributing to the 1974 LP Dream House 78' 17".

On his return to Buffalo in the early 1970s, Hassell was introduced to the music of Indian Pandit Pran Nath, a specialist in the Kiranic style of singing.

His 1981 release, Dream Theory in Malaya, led to a performance at the first World of Music, Arts and Dance (WOMAD) Festival, organized by Peter Gabriel.

[7] Both on record and during live performances, Hassell made use of western instruments—keyboards, bass, electric guitar, and percussion—to create modal, hypnotic grooves, over which he often played microtonally-inflected trumpet phrases in the style of Nath's Kiranic vocals.