Johann Sebastian Demar was born in the Bavarian place Gauaschach on June 29th, 1763. He originates from a musician family, his father was a music teacher, his brother Joseph was a violinist in the chapel of the grand duke of Würzburg.
Demar studied with Franz Xaver Richter in Strasbourg and then became an organist and music teachers in Weißenburg (Unterelsaß). Later he travelled to Vienna and became a pupil of Haydn. Demar went 1788 to Paris and 1789 as music teachers set up in Orléans. 1806 he founded the Société of the Concerts par Abonnement which he himself conducted and which took an important role in the cultural life of the town Orleans. A number of years Demar was director of the music education of the Garde Nationale d'Orléans. He became an organist 1815 to Saint Paterne in Orléans. Demar died in Orléans on July 25th, 1832.