Mozart started a series of concerts in which he played his own piano concertos, conducting from the keyboard. He met the composer Joseph Haydn and the two men became great friends, often playing together in a string quartet. Haydn said to Leopold Mozart one day: "Before God and as an honest man I tell you that your son is the greatest composer known to me either in person or by name. He has taste, and what is more, the most profound knowledge of composition." Mozart was in the same Masonic Lodge as Haydn, and he dedicated some of his string quartets to him.