The string quartets, the first of which he wrote during his Italian journey of 1770, are in his early period slight and unpretentious but lucid and delicate compositions, in which we may trace influences of Sammartini and Boccherini. From 1773 on, however, the influence of Haydn’s genius is apparent. By 1781, when Mozart took up his residence in Vienna, quartet-playing had become one of the favorite pastimes of musical amateurs. Haydn was the acknowledged leader in this popular field and ‘whoever ventured on the same field was obliged to serve under his banner.’ During the period of 1782 to 1785 Mozart wrote a series of six quartets, which he dedicated to that master ‘as the fruit of long and painful study inspired by his example.’ After playing them over at Mozart’s house (on such occasions Haydn took the first violin part, Dittersdorf the second, Mozart the viola, and Vanhall the 'cello) Haydn turned to Leopold Mozart and said: ‘I assure you solemnly and as an honest man that I consider your son to be the greatest composer of whom I have ever heard.’ Like Haydn and Boccherini, Mozart was commissioned to write some quartets for the king of Prussia (William II), and, since his royal patron himself played the 'cello, he cleverly emphasized that instrument without, however, depriving the other instruments of their independent power of expression. Mozart’s partiality for quartet writing is evident from the many sketches in that form which have been preserved. They are among the masterpieces of chamber music, as are also his string duos, trios, and, especially, his four great string quintets. The celebrated one in G minor is, as Jahn says, a veritable ‘psychological revelation.’ Few pieces in instrumental music express a mood of passionate excitement with such energy.’ Mozart’s concertos for the piano and also those for the violin were written primarily for his own use. The best of them date from the period preceding his Paris journey, when he expected to make practical use of them, for he was a virtuoso of no mean powers on both instruments. There are six concertos for either instrument, every one full of pure beauty and a model of form. In them he substituted the classic sonata form for the variable pattern used in the earlier concertos, and hence he may be considered the creator of the classic concerto, his only definite contribution to the history of form. They are not merely brilliant pieces for technical display, but symphonic, both in proportion and import. In them are found some of the finest moments of his inspiration. ‘It is the Mozart of the early concerti to whom we owe the imperishable matter of the Viennese period,’ says Mr. Hadow, ‘and the influences which helped to mold successively the style of Haydn, Beethoven, and Schubert.’