Mozart KV 444 (425a) - Symphony No. 37 in G major (Michael Haydn) The so-called Symphony No. 37 in G major, K. 444/425a, is an introduction by Wolfgang Amadeus Mozart to a symphony in G by Michael Haydn. The complete symphony was for a long time believed to be a work by Mozart, but is now known to have actually been mostly written by Michael Haydn, being his Symphony No. 25 in..