Intent on developing the reputation he had won in Vienna, Beethoven undertook an extensive tour ending in Berlin, home to the cello-playing Frederick William II. There he unveiled his Sonatas for Piano and Cello, Op. 5 with one of the famed Duport brothers playing cello. These are revolutionary works, with neither instrument subservient and the piano fully independent, for which in the 1790s there was no precedent. Beethoven also wrote vivacious variations on operatic music by Mozart where light-hearted playfulness and dramatic rivalry are energising features.