guillaume dufay (pronounce "ghee-oam doo-fye", sometimes spelt du fay) (born beersel? 5 august 1397?; died cambrai, 27 november 1474) was a franco-flemish composer and music theorist of the early renaissance. he was the most important composer of his time. he belonged to the group of composers known as the burgundian school. he had more influence on music in europe than any other composer of the 15th century.