At the end of the seventeenth century the concert-symphony, as we now understand that term, was unknown; at the end of the eighteenth it was the most important form of purely orchestral music, and a moderate estimate is that considerably more than 1,500 such works had been written. The later and mature symphonies by Haydn and Mozart were then in existence, and the next quarter-century was to see the advent of all the Beethoven and of most of the Schubert symphonies. If we base our knowledge of symphonies only on those which are commonly played in our concert-rooms, we might reasonably suppose that this form of music came into being rather suddenly during the last quarter of the 18th century, and that Haydn and Mozart were its joint creators. The story of the symphony, however, begins before either of these two composers was born, and the establishment and consolidation of this vital orchestral form belongs to a period which predates that in which the mature and influential symphonies of both Haydn and Mozart made their appearances.