The promise of a change in style, evident in the Kreutzer Sonata (1803) and in the pianoforte concerto in C minor, is practically completed in the Eroica Symphony (1804)--a change of which Beethoven was fully conscious and which he described in a letter as ‘something new.’ It began the second period, lasting until 1814, to which belongs a striking and remarkable group of works. In the long list are six symphonies, the third to the eighth inclusive, the opera _Fidelio_ with its four overtures, the Coriolan overture, the Egmont music, the pianoforte concertos in G and E flat, the violin concerto, the Rasoumowsky quartets, and a dozen sonatas for the piano, among which are the D minor and the Appassionata. It was a period characterized by maturity, wealth of imagination, humor, power, and individuality to a marvellous degree. If Beethoven had done nothing after 1814, he would still be one of the very greatest composers in the field of pure instrumental music. His ideas increase in breadth and variety, the designs grow to magnificent proportions, the work becomes more harmonious and significant, touching many sides of thought and emotion. In this period he broke through many of the conventions of composition, as, for example, the idea that certain musical forms required certain kinds of treatment. The rondo and scherzo, formerly always of a certain stated character, were made by him to express what he wished, according to his conception of the requirements of the piece. Likewise the number of his movements was determined by the character and content of the work, and the conventional repetition of themes was made a matter of choice. Moreover, the usual method of key succession was used only if agreeable to his idea of fitness. In the great majority of sonatas by Haydn and Mozart, if the first theme be given out in a major key, the second is placed in the dominant; or, if the first is in minor, the second would be in the relative major. Beethoven makes the transition to the dominant only three times out of eighty-one examples, using instead the subdominant, the third above, or the third below. He changes also from tonic major to tonic minor, and _vice versa_. With him the stereotyped restriction as to key succession was no longer valid when it conflicted with the necessity for greater freedom.