In the second half of the 18th century, the string quartet developed into the most important genre of chamber music for string instruments. Mozart’s early string quartets are in three movements (he later added a rondo to his first quartet, K. 80). By the time of his stay in Vienna in the autumn of 1773, Mozart had become acquainted with the innovative quartets of Joseph Haydn; all of Mozart’s later string quartets follow Haydn’s model in having four movements. Mozart expressed his gratitude to Haydn by dedicating to him the quartets of his Opus 10. Like Haydn, Mozart sought an egalitarian treatment of all instruments, for example through the use of contrapuntal techniques. The last three quartets—K. 575, K. 589, and K. 590—feature technically demanding, sometimes soloistic cello parts and were intended for Frederick William II of Prussia, who was himself an accomplished cellist. Mozart also composed several highly individual quartets for a woodwind instrument and strings.