The French organ school formed in the first half of the 17th century. It progressed from the strict polyphonic music of Jean Titelouze (c. 1563–1633) to a unique, richly ornamented style with its own characteristic forms that made full use of the French classical organ. Instrumental in establishing this style were Louis Couperin (c. 1626–1661), who experimented with structure, registration and melodic lines, expanding the traditional polyphonic forms, and Guillaume-Gabriel Nivers (1632–1714), who established the distinct forms and styles of what was to become the French organ tradition.