A new element came into music, incompatible with fugue, requiring a different form of expression, and incapable of combination with fugue. That element was the people's song, with its symmetrical cadences and its universal intelligibility. Let the reader take any one of the Mozart sonatas, and play the first melody he finds--he will immediately see that here is something for which no place could have been found in a fugue, nor yet in its complement, the prelude of Bach's days. The same is true of many similar passages in the sonatas of Haydn. Music had now found the missing half of its dual nature. For we must know that in the same manner as the thematic or fugal element in music represents the play of musical fantasy, turning over musical ideas intellectually or seriously; so there is a spontaneous melody, into which no thought of developing an idea enters. The melody flows or soars like the song of a bird, because it is the free expression, not of musical fantasy, as such (the unconscious play of tonal fancy), but the flow of _melody_, _song_, the soaring of spirit in some one particular direction, floating upon buoyant pinions, and in directions well conceived and sure. The symmetry of the people's song follows as a natural part of the progress. The spontaneous element of the music of the northern harpers now found its way into the musical productions of the highest geniuses. Henceforth the fugue subsides from its pre-eminence, and remains possible only as a highly specialized department of the general art of musical composition, useful and necessary at times, but nevermore the expression of the unfettered fancy of the musical mind. The discovery of the secret of musical contrast, in the types of development, the _thematic_ and the _lyric_, led to the creation of a new form, in which they mutually contrast with and help each other. That form was the Sonata, which having been begun earlier, was developed further by the sons of Bach, but which received its characteristic touches from the hands of Haydn and Mozart. This was the crowning glory of the eighteenth century--the sonata. A form had been created, into which the greatest of masters was even then beginning to breathe his mighty soul, producing thereby a succession of master works, which stand without parallel in the realm of music. CHAPTER XXIII. JOHN SEBASTIAN BACH.