He commenced his musical career as a violinist and a singer. His orchestral symphonies were for violins (for strings), with occasional seasoning from the brass and wood wind. The constant study of the violin led to modifications in his style, and evolved first, the string quartette in the form which has always remained standard. The symphonies are only larger string quartettes, for, in the order of the themes, the general manner of treating them and the principles of contrast or relief which actuated them, the quartettes are sonatas, as also are the symphonies. Haydn gave the sonata form its present shape. The insertion of a second theme in the first movement, and the principle of contrasting this second theme with the first in such a way that the second theme is generally lyric in style, or at least tending in that direction, was Haydn's. He also developed the middle part of the sonata into what is known as the "elaboration," "_Durchfuehrungssatz_". The cantabile slow movement, modeled somewhat after the Italian cantilena, was his. Mozart and Beethoven did wonders with it later, but the suggestion was Haydn's. The endless productivity, the constant succession of new pieces demanded, led to a somewhat systematic proceeding in their production, and so the form and the method of the sonata became stereotyped. All the instrumental movements of this time, whenever there was any serious intention, assumed the form of sonatas; _i.e._, of the instrumental sonatas--the symphony and the quartette.