Guillaume de Machaut
Machaut worked for John of Luxemburg, king of Bohemia, around 1323. The king travelled around Europe, fighting, and Machaut went with him, working as his secretary. After 1330 he became canon of several cathedrals. After John of Luxemburg died during a battle in 1346, Machaut worked for John's daughter Bonne (who later married King John II of France), then King Charles the Bad of Navarre, Charles of Normandy who became King Charles V in 1364 and the King of Cyprus. He also worked for wealthy dukes. With all that work it is surprising that he had time to compose. He seems to have spent his later years living in Rheins, working on his compositions.