The six string quartets, K. 155–160, were composed by Wolfgang Amadeus Mozart in late 1772 and early 1773 when Mozart was sixteen and seventeen years of age. Because they were composed in Milan while he was working on his opera Lucio Silla, they are popularly known as the Milanese Quartets. Before this set was composed, Mozart had written one earlier string quartet, so these six quartets are ordinally numbered from No. 2 to No. 7. The quartets are written in a plan of keys of D-G-C-F-B♭-E♭ following the circle of fifths.
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