The second theme, as time went on, became more and more individualized and, as it assumed more distinct rhythmic and melodic characteristics, it lent itself more freely to logical development, like the principal subjects, became in fact a real ‘subject’ on a par with the first. With Stamitz and the Mannheim school, at last, we meet the idea of _contrast between the two themes_, not only in key but in spirit, in meaning. As with characters in a story, these differences can readily be taken hold of and elaborated. The themes may be played off against each other, they may be understood as masculine and feminine, as bold and timid, or as light and tragic--the possibilities of the scheme are unlimited, the complications under which an ingenious mind can conceive it are infinite in their interest. Thus only, by means of _contrast_, could states of mind be translated into musical language, thus only was it possible to give voice to the deeper sentiments, the new feelings that were tugging at the heart-strings of Europe. Only with this great principle of emotional contrast did the art become receptive to the stirrings of _Sturm und Drang_, of incipient Romanticism, thus only could it give expression to the graceful melancholy of a Mozart, the majestic ravings of a Beethoven. III Having given an indication of the various stages through which the sonata form passed, we may now speak of the men who developed it. We are here, of course, concerned only with those who cultivated the later and eventually universal German type. In the band of musicians gathered about the court of Frederick the Great we find such pioneers as Joachim Quantz, the king’s instructor on the flute;[25] Gottlieb Graun, whose significance as a composer of symphonies, overtures, concertos, and sonatas is far greater than that of his brother Karl Heinrich, the composer of _Der Tod Jesu_; and the violinist Franz Benda, who was, however, surpassed in musicianship by his brother Georg, _kapellmeister_ in Gotha. All of these and a number of others constitute the so-called Berlin school, whose most distinguished representative by far was Carl Philipp Emanuel Bach, the most eminent of Johann Sebastian’s sons. He has been called, not without reason, the father of the piano sonata, for, although Kuhnau preceded him in applying the form to the instrument, it is he who made it popular, and who definitely fixed its pattern, determined the order of its movements--Allegro; Andante or Adagio; Allegro or Presto--so familiar to all music-lovers.