Answer: 5 years old
Wolfgang Amadeus Mozart was born in Austria in 1756, in a family surrounded by music, perhaps that is why he was a prodigious child who already at 3 years old played the piano to accompany his father's violin melodies.
In his childhood, Mozart was known as a naughty and jovial child, showing from an early age the mastery of instruments such as piano and violin, something out of the ordinary for a child.
In fact, at the age of 5 he composed his first piano works, at the age of 9 he composed symphonies, and at 12 he composed entire operas. That is why he was famous throughout Europe.
Mozart lived and worked intensely during his short life, because he died at an early age, at age 35 in 1791.