Original: During this period he probably wrote his mass based on L'homme armé, as well as the chanson on the same song; the latter composition may have been inspired by Philip the Good's call for a new crusade against the Turks, who had recently captured Constantinople.
Simplified: During this period Dufay probably wrote his mass based on the song L'homme armé, as well as the chanson based on the same song. Maybe he wrote this when Philip the Good called for a new crusade against the Turks, who had recently captured Constantinople.