Thus there were no string-quartets, before Haydn - at least none that can be distinguished from: symphonies for string-band.
His most important works were the Missa hispanica, which he exchanged for his diploma at Stockholm, a Mass in D minor, a Lauda Sion, a set of graduals, forty-two of which are reprinted in Diabelli's Ecclesiasticon, three symphonies (1785), and a string quintet in C major which has been erroneously attributed to Joseph Haydn.
To this period belong five Masses, a dozen operas, over thirty clavier-sonatas, over forty quartets, over a hundred orchestral symphonies and overtures, a Stabat Mater, a set of interludes for the service of the Seven Words, an Oratorio Tobias written for the Tonkiinstler-Societe t of Vienna, and a vast number of concertos, divertimenti and smaller pieces, among which were no less than 175 for Prince Nicholas' favourite instrument, the baryton.
There can have been little personal intercourse between them, for Haydn was rarely in the capital, and Mozart seems never to have visited Eisenstadt; but the cordiality of their relations and the mutual influence which they exercised upon one another are of the highest moment in the history of 18th-century music. " It was from Haydn that I first learned to write a quartet," said Mozart; it was from Mozart that Haydn learned the richer style and the fuller mastery of orchestral effect by which his later symphonies are distinguished.
Haydn, thus released from his official duties, forthwith accepted a commission from Salomon, the London concertdirector, to write and conduct six symphonies for the concerts in the Hanover Square Rooms. He arrived in England at the beginning of 1791 and was welcomed with the greatest enthusiasm, receiving among other honours the degree of D Mus.