Jakob-Ignaz-Sebastian Demar (29 June 1763 – 25 July 1832) (often wrongly called Jean-Sébastien Demar or much more recently Jacques-Sébastien) was a German pianist, composer, conductor, music teacher and organist.
Born in the vicinity of Gauaschach, now part of Hammelburg, district of Bad Kissingen in Lower Franconia (Germany), on 29 June 1763, he died in Orléans, on 25 July 1832. He was the son of music teacher Sebastien Demar and his wife Dorothée Zugis.Born into a family of musicians, he was first trained at the Strasbourg Cathedral by the Kapellmeister and composer Franz Xaver Richter, representative (in the same way as Johann Stamitz) of the Mannheim School. Then he became organist in Wissembourg, (Alsace). He also traveled to Vienna (Austria) to further his studies in the field of composition, with Joseph Haydn. He arrived in Paris in 1788 and settled in Orléans in 1789, shortly before the Revolution. Demar did a lot for music in the city, where he first directed the music of the 88th Regiment (he was in place on 23 December 1791), then of the National Guard. In 1799, he was appointed by the municipality to play the organ as an amateur at Republican festivals, in the various "temples" (the old churches) where they were held: the plain-song gave way to the "war song".