The reader will note that the division of these periods is not based on chronological, but artistic grounds; and hence, in respect of years, they overlap. The most famous writer of the first period was Johannes Okeghem, born between 1415 and 1430, in East Flanders. He studied under Binchois, a contemporary of Dufay, at Antwerp, was a singer in the service of Charles VII. of France in 1444, was made by Louis XI. Treasurer of the Cathedral of St. Martin's at Tours, and died there about 1513. A considerable quantity of his music has been preserved. It is notable chiefly for its technical skill; and during his life Okeghem was the most famous teacher of his day. His most noted pupil was Antoine Brumel (1460-1520), whose personal history is lost, though many of his masses and motets are preserved. Jacob Hobrecht (1430-) achieved great celebrity. Eight of his masses are extant. As I have said in another account of the Netherlands school, "It is the prevailing influence of one or two masters in each period that marks its extent. Its character was formed by that influence, and salient features of the style of each period may be fairly distinguished. The first period was marked by the extreme development of the 'canon.'" I have already endeavored to explain the nature of canonic writing. If the reader will bear in mind that it is the most rigid form of imitation, requiring the original melody to be imitated throughout in the subsidiary parts, he will not go astray. Okeghem and his contemporaries completely explored the resources of canonic writing. They invented all kinds of canons. They originated the 'crab' canon, in which the part sung by the second voice was the first voice part written backwards. Here is an example taken from a text-book by Dr. Bridge:-- 'CRAB' CANON, OR CANON RECTE ET RETRO. [Music: _Begin at either end; play either forward or backward._]