Leopold realized that he could earn a substantial income by showcasing his son as a Wunderkind in the courts of Europe. Mozart soon gained fame as a musical prodigy capable of such feats as playing blindfolded or competently improvising at length on difficult passages. His older sister Maria Anna (Nannerl) was a talented pianist and accompanied her brother on the earlier tours. Mozart wrote a number of piano pieces, in particular duets and duos, to play with her. On one occasion when Mozart became very ill, Leopold expressed more concern over the loss of income than over his son’s well-being.

During his formative years, Mozart completed several journeys throughout Europe, beginning with an exhibition in 1762 at the Court of the Elector of Bavaria in Munich, then in the same year at the Imperial Court in Vienna. A long concert tour spanning three and a half years followed, taking him with his father to the courts of Munich, Mannheim, Paris, London, The Hague, again to Paris, and back home via Zürich, Donaueschingen, and Munich. They went to Vienna again in late 1767 and remained there until December 1768.

After one year in Salzburg, three trips to Italy followed: from December 1769 to March 1771, from August to December 1771, and from October 1772 to March 1773. During the first of these trips, Mozart met Andrea Luchesi in Venice and G.B. Martini in Bologna and was accepted as a member of the famous Accademia Filarmonica. A highlight of the Italian journey, now an almost legendary tale, occurred when he heard Gregorio Allegri’s Miserere once in performance in the Sistine Chapel then wrote it out in its entirety from memory, only returning to correct minor errors; he thus produced the first illegal copy of this closely-guarded property of the Vatican [source documents].

On July 3, 1778, accompanied by his mother, Mozart began a tour of Europe that included Munich, Mannheim, and Paris, where his mother died.

During his trips, Mozart met a great number of musicians and acquainted himself with the works of other great composers. A particularly important influence was Johann Christian Bach, who befriended Mozart in London in 1764–65. Bach’s work is often taken to be an inspiration for the distinctive surface texture of Mozart’s music, though not its architecture or drama.

Even non-musicians caught Mozart’s attention. He was so taken by the sound created by Benjamin Franklin’s glass harmonica that he composed several pieces of music for it.