In 1964 he moved to New York City, where he studied with Frederick Zimmermann and played in Roy Eldridge's band.

In addition to jazz, their repertoire ranged from "the baroque of Bach, Scarlatti, Corelli and Couperin through the lush music of Tchaikovsky, Strauss and Debussy, to arrangements of contemporary composers such as the Beatles and Bobbie Gentry.

[2] In 1971 Gregg, Jack DeJohnette, Bob Moses, Harold Vick and Juma Santos formed Compost, a jazz fusion band.

[4] In 1976 Gregg left the United States and subsequently lived in Europe, eventually settling in Paris.

[1] Gregg, pianist Arthur Satyan and drummer Steve Phillips formed a trio called Three Wheel Drive that played "authentic jazz" in Lebanon from 1996 until 2004.