Many of the major 15th- and 16th-century composers of the Franco-Flemish School—a current of vocal polyphony that played a central role in European art music of the time—were born and bred in the portion of the Low Countries that is situated in present-day Belgium, often in Hainaut. The late medieval composer and music theorist Johannes Ciconia (c. 1370–1412) had been born in Liège, but like many later Flemish polyphonists he spent much of his life working in Renaissance Italy. While it remains unclear why Flemish and other Netherlandish musicians exerted such a strong influence on Renaissance music throughout Europe (with a particularly strong axis developing between Liège and Rome), one possibility is the emphasis that was placed locally on music theory. Guillaume Dufay (c. 1397–1474), who was born near Brussels (he moved as a child to Cambrai, and also worked in Italy), was a key figure of the early 15th-century Burgundian School, and he was considered by his contemporaries to be the leading composer of the age. Another influential figure was Gilles Binchois (c. 1400–1460): probably born in Mons (or nearby Binche) he moved to Lille, the largest city of what is now French Flanders, and unlike many of his contemporaries, he maintained professional connections with the Burgundian court throughout his life. Johannes Ockeghem (c. 1410–1497) is also considered one of the leading composers of the 15th century; a native of Hainaut, he spent most of his career working for the French court.