It would be foolish to attempt an analysis of what may be its emotional content. It calls for no such analysis, but stands as another instance of the strange power Mozart’s music has to satisfy of itself alone. It must remain, like his other work, mysterious and of secret origin. Only one section is given a key-signature. The others are without harmonic limitation. Perhaps the opening section, and the brief part of it repeated at the end, are the most impressive. The motive out of which they are built is of unfathomable significance; their harmonies rise and fall as slowly and mysteriously as the tide. Of the quality of other more melodious sections, of the occasional charm and grace that here and there rise, as it were, on the wings of light; of the passionate harmonies that die away into silence before the slow opening motive returns inexorably, nothing can be said. There comes over it in memory the light that never was on land or sea. It is a poet’s dream. III We have now to consider the pianoforte concertos which as a whole may be taken to be the finest of his works for the instrument. They were written primarily for his own use, seventeen of them in Vienna between 1783 and 1786, some earlier, however, and a few later. They are concertos in the modern sense, not like the concertos of Sebastian Bach. In the latter we find the clavier treated in much the same style as the orchestra or the _tutti_, as it was, and still is, generally called. In the Mozart concertos, on the other hand, the solo instrument is given a rôle which will show off to the best its peculiar qualities. The Vivaldi form of concerto, such as Bach used, was a modified rondo; that is to say, there was one chief subject, usually announced at the beginning by the tutti. This subject properly belonged to the tutti, and the solo instrument was given various episodes of contrasting material, between which the orchestra usually was introduced with ritornelles based upon the chief subject. The whole was a sort of dialogue between soloist and orchestra. The form of the concerto which Mozart used was clearly as follows: an expanded triplex form for the first movement, a slow movement in song form, and a rondo of the French type for the finale. Moreover, he used the solo instrument not only alone, but with the orchestra; in such cases writing a brilliant sort of _fioritura_ for it, which added a special and distinct color to the ensemble. Such a form of concerto was apparently first employed by Christian Bach in London. From him Mozart learned the use of it. He was not, therefore, as has often been stated, the true ‘father’ of the modern concerto. Nevertheless it was he who first used the form with enduring success, and it may be considered as his special contribution to the standard musical forms.