During his two-years scholarship at Berklee College of Music, Boston, Valentin Gregor performed with accomplished musicians like Stephane Grapelli, Herb Geller, Ed Harris, Garrison Fewell, Duduka da Fonseca, Hans Glawischnig and Nicolas Simion. In March 2000, he joined the Ken Hatfield Quartet in New York to record an album that won him great appreciation as a jazz violin soloist. No less successful were his live performances with the award-winning jazz singer Dane Vannatter in New York's Manhatten Town Hall (1997).
When he returned from Berklee, he moved to Berlin to perform both as solo violinist and musical director in various theatres and band projects. He performed many years at Pomp Duck and Circumstance and was musical director of the Deutsche Theater Berlin. In 2004 he joined ELO II, the successor of the Elecric Light Band, as their new solo violinist. In the same year he also released his first album "Smellodie" with the Valentin Gregor Quartet and in 2007 "The Berlin Songbook" with Victor Alcántara (p) in the duo Berlynatic Arkestra.