Simplify the following text for a Grade 16 native English-speaking person.
Original: Johannes Ockeghem ( also Jean de , Jan ; surname Okeghem , Ogkegum , Okchem , Hocquegam , Ockegham ; other variant spellings are also encountered ) ( 1410 â `` 1425 , Saint-Ghislain , Belgium -- February 6 , 1497 , Tours , France ) 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 Dufay and Josquin des Prez .
Simplified: Johannes Ockeghem ( born Saint-Ghislain , near Mons , Belgium about 1410 ; died Tours , France , 6 February 1497 ) , was the most famous composer of the Franco-Flemish School ( from around the area which is now Belgium ) in the last half of the 15th century , and is often thought of as the most important composer between Dufay and Josquin des Prez .