Did Mozart compose all his works alone?

Wolfgang Amadeus Mozart, composer of the Classical Period -

Born - 27th of January, 1756 in Salzburg, Austria

Died - 5th of December, 1791 in Vienna, Austria

Mozart married Constanze Weber, the younger sister of his first love, Aloysia, who had turned him down.

Major works include - 4 Operas, 21 Piano concertos, 5 Violin concertos, Concertos for Clarinet and other wind instruments, 41 Symphonies, 24 String quartets and other chamber music, 17 Masses.