Wolfgang Amadeus Mozart's Piano Sonata No.

7 in C major, K. 309 (284b) (1777) is a piano sonata in three movements: A typical performance takes about 16 minutes.

[citation needed] The work was composed during a journey to Mannheim and Paris in 1777-78.

In a letter to his father dated October 24 1777, Mozart describes a concert where he played "a magnificent sonata in C major with a closing rondo, my own invention",[2] suggesting that the sonata was completed by October 1777.

[3] Upon reviewing a copy of the manuscript, Mozart's father Leopold wrote that it was "a strange composition.