g minor has been considered the key through which wolfgang amadeus mozart best expressed 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. though mozart touched on various minor keys in his symphonies, 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 alto. another convention of g minor symphonies observed in mozart's no. 25 and mozart's no. 40 was the choice of e-flat major, the subdominant of the relative major b, for the slow movement, with other examples including joseph haydn's no. 39 and johann baptist wanhal's g-minor symphony from before 1771.