 The surviving works include the keyboard sonatas written in Paris, London and The Hague, four symphonies, various arias, the assorted music written for the Prince of Orange, a Kyrie, and other minor pieces.Mozart's career as a symphonist began in London where, in addition to the direct influences of Abel and J.C. Bach, he would have heard symphonies from leading London composers including Thomas Arne, William Boyce and Giuseppe Sammartini—"a nearly ideal introduction to the genre", according to Zaslaw.The earliest symphonies, Zaslaw points out, while not in the same class as the later Mozart masterpieces, are comparable in length, complexity and originality to those written at the same time by the acknowledged symphonic masters of the day.