Gottfried van Swieten (1723-1803) was a wealthy patron of several Classical era composers including Mozart, Haydn and Beethoven.
A music lover and amateur composer, van Swieten had collected manuscripts of Bach and Handel during his years in Berlin. After moving to Vienna, van Swieten and Mozart became friends. Mozart visited him regularly and enjoyed playing from the manuscripts of Handel, J.S. Bach and his sons.
In a letter Mozart penned to his father in 1782, he wrote, “I go every Sunday at twelve o'clock to the Baron van Swieten, where nothing is played but Handel and Bach. I am collecting at the moment the fugues of Bach—not only of Sebastian, but also of Emanuel and Friedemann.”
The Bach effect is evident in many of Mozart’s greatest works including the C Minor Mass and the chorale prelude sung in The Magic Flute.