G minor
Wolfgang Amadeus Mozart thought that G minor was the most suitable key for showing sadness and tragedy, and many of his minor key works are in G minor, such as the Piano Quartet No. 1 and the String Quintet in G minor. G minor is the only minor key he used as a main key for his numbered symphonies (No. 25, and the famous No. 40). In the Classical period, symphonies in G minor almost always used four horns, two in G and two in B-flat alto. G minor symphonies like Mozart's No. 25 often used E flat major for the slow movement, including Haydn's No. 39 and Vanhal's G minor symphony from before 1771 (Bryan Gm1).