Among the innovations made by Beethoven, may be mentioned the extension of key relationship, which before him was not recognized. He broke down the restrictions that governed transitions. Here he was revolutionary. The principles of his harmonic combinations have been thus formalized by Mr. Dannreuther: "(_a_) Any chord can succeed immediately any chord belonging to another tonality, no matter how remote, provided they have one note in common, even if it be only harmonically so. (_b_) It is possible to produce quick harmonic progressions into the most remote tonalities by means of chromatic and enharmonic changes in individual parts, which are made to move on step by step, thus building a sort of chromatic or enharmonic bridge." And Mr. Dannreuther cites as instances, the connection between variations 32 and 33 in Op. 120; and the return from B major, at the close of the "working out," to the first subject in B-flat major in the first movement of Op. 106. Before the time of Beethoven composers of sonatas and symphonies had generally confined themselves to a narrow range of keys. The theme of the first movement was given out in the tonic, and if it was major, it was answered by the second theme in the fifth above; that is to say, if the sonata were in C, the second subject would be in G. If the movement were in the minor, the second subject would be in the relative major: i.e. the second theme of a movement in C minor would be in E flat. So too the key of the second movement was usually restricted, although sometimes there was a little more liberty. The painstaking Grove has examined the eighty-one works of Beethoven in sonata form. The transition to the dominant occurs only three times; to the subdominant nineteen times; to the third below thirty times. "His favorite change was evidently to the submediant or third below--that is to say, to a key less closely related to the tonic and more remote than the dominant key." He makes it as early as Op. 1, No. 2. [Illustration: BUST OF BEETHOVEN. Made by Franz Klein, after the Life-mask taken by him in 1812. (See page 327.)]