French organist and composer; born at Paris. He studied music under Bordier and Forqueray, the organist, the latter being his uncle, and at fifteen years of age sought the post of organist at St. Andre-des-Arcs' parish church and obtained it against strong competition. He is said to have astonished Couperin and other noted organists of the time by playing when he was only thirteen an extemporaneous Te Deum, with great brilliancy and precision. He was joint-organist at Notre Dame Cathedral in 1772, organist at the Church of St. Sulpice in 1783, Court organist in 1789 and organist of the Church of the Invalides in 1807. He was also organist at the Paris Conservatory and taught at the Royal School of Music there. He died in Paris. Sejan composed fugues; six violin sonatas; three piano trios; also much other music for piano and violin and works for the organ.