Charles d'Helfer
Charles d'Helfer (1598–1661) was a French baroque composer and "maître de musique" at Soissons Cathedral. His masses follow a strict one syllable per note style. He is best remembered for his requiem for four voices of 1656 which was used for the funeral of composer Michel Richard Delalande in 1726 and was the basis of Julien-Amable Mathieu (1734-1811) and François Giroust's requiem mass for Louis XV in 1775. Sources. Jean-Paul C. Montagnier, "The Polyphonic Mass in France, 1600-1780: The Evidence of the Printed Choirbooks," Cambridge: Cambridge University Press, 2017.