A son was born in 1783, who died in the same year, and in the summer a visit was paid to Salzburg. A mass, which Mozart had vowed in his heart before his marriage if he succeeded in taking Constanze there as his wife, was performed; he wrote duets for violin and viola to help Michael Haydn, who was prevented by sickness from satisfying the Archbishop's command; he sketched a part of an opera, "L'Oca del Cairo." In one way the visit was a disappointment. Neither Leopold nor Marianna was really fond of Constanze, and Mozart was displeased because none of the trinkets that had been given him in his youth were offered to his wife. He returned to Vienna in October. In 1785 the father returned the visit. He wept for joy at hearing Wolfgang play the pianoforte concerto composed for the blind pianist, Marie Paradies; he heard string quartets of his son played by Haydn, Dittersdorf, Wolfgang and Vanhall; and Haydn said to him, "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." Influenced by his son he became a Freemason. There were secret associations, brotherhoods of all descriptions, more or less closely allied to Freemasonry, throughout Germany during the latter half of the eighteenth century. Many wished to join together in fighting for liberty of conscience and independence of thought; and, as Herder, Wieland, Goethe, they saw in Freemasonry "a means of attaining their highest endeavors after universal good." In Vienna nearly all the distinguished leaders of thought were Freemasons; the lodges were fashionable, and in 1785 the Emperor Joseph placed them under the protection of the state, although he first reduced the number. It is not surprising that Mozart, with his love for humanity, his warm sympathies for all that is good and noble, should enter eagerly into masonic ties and duties. He contemplated the founding of a secret society of his own. His lodge was the oldest in Vienna, "Zur gekrönten Hoffnung," and for this lodge he wrote vocal and instrumental works, one of which, the "Trauermusik" is of great beauty and originality.