Johannes Ockeghem (also Okeghem, Ogkegum, Okchem, Hocquegam, Ockegham) (1410?-1497) was the most famous composer of the Franco-Flemish School in the last half of the 15th century, and is often considered the most influential composer between Guillaume Dufay and Josquin des Prez. In addition to being a renowned composer, he was also an honored singer, choirmaster, and teacher. Ockeghem is believed to have been born in the Walloon city Saint-Ghislain, Netherlands (now Belgium). His birthdate is unknown; dates as early as 1410 and as late as 1430 have been proposed. A strong influence on Josquin des Prez and the subsequent generation of Netherlanders, Ockeghem was famous throughout Europe for his expressive music, though he was equally renowned for his technical prowess. Two of the most famous contrapuntal achievements of the 15th century include his Missa prolationum, which consists entirely of mensuration canons, and the Missa cuiusvis toni, designed to be performed in any of the different modes.