Concert Spirituel
Mozart was recruited by the director of the "Concert Spirituel", Joseph Legros, to write some choruses, K. 297a, which were played without giving credit to Mozart. Then Mozart wrote a "Sinfonia concertante in E flat major" K. 297b, for a group of four wind players from Mannheim, which he sold to Legros without keeping a copy. Legros never had it copied for performance, and the work became considered "lost". Mozart at last enjoyed one great success at the "Concert Spirituel" as a composer with his "Symphony No. 31 in D", K. 297 ("Paris Symphony"), performed on June 18, 1778 "to unanimous acclaim".