 As a Kodály disciple, he was involved for two years in research about Gypsy musical culture and published several articles on this subject.After the Hungarian Revolution of 1956, Hajdu escaped to Paris and continued his studies at the Paris Conservatoire with Darius Milhaud (composition) and Olivier Messiaen (philosophy of music), obtaining the 1st prize in the discipline.Among his class mates were Gilbert Amy, William Bolcom, Philip Corner and Paul Méfano.