In 1762, at the age of six, Mozart was presented as a performer at the imperial court in Vienna. By that time, he was already a budding composer and an accomplished keyboard performer, and soon after he would embark on a three-year tour of Europe, performing with his sister.

Mozart loved to play Billiards, and would sometimes play all night, composing symphonies as he played.

Mozart disliked prima donna Adriana Ferrarese del Bene, da Ponte's arrogant mistress for whom the role of Fiordiligi in Così fan tutte had been created. Knowing her idiosyncratic tendency to drop her chin on low notes and throw back her head on high ones, Mozart filled her showpiece aria Come scoglio with constant leaps from low to high and high to low in order to make Ferrarese's head "bob like a chicken" onstage.

The Magic Flute is noted for its prominent Masonic elements, although some scholars claim that the Masonic influence is exaggerated. Schikaneder (the librettist) and Mozart were Masons as was Ignaz Alberti, engraver and printer of the first libretto.

Mozart composed Bastien und Bastienne at the age of twelve, and it premiered in Vienna in 1768. It was based upon The Loves of Bastien and Bastienne (Les amours de Bastien et Bastienne) by Marie-Justine-Benoîte Favart and Harny de Guerville.

Mozart dedicated six string quartets (1782-85) to the Austrian composer Franz Joseph Haydn, one of the greatest masters of classical music. The quartets are a testament to Haydn's influence on the younger Mozart.

First proposed in 1993 by Alfred A. Tomatis, the "Mozart Effect" is the belief that listening to Mozart's music can temporarily boost a person's IQ. Mozart has even been credited with boosting the milk production of cows and helping microbes break down sewage waste.

By the age of 3, Mozart had already learned to play the clavier, an old-fashioned stringed instrument that also had a keyboard. By the age of 5, he was playing the harpsichord and violin as well as a professional.

Mozart's main rival was the Italian composer Antonio Salieri, who wrote more than 40 operas. Several years after Mozart's death, rumors began to surface that Salieri had poisoned him. Although most historians dismiss these charges, some researchers have suggested that Mozart may in fact have died from mercury poisoning.

Bastien and Bastienne uses the same opening theme as Beethoven's Symphony No. 3, the Eroica. It is doubtful that Beethoven was familiar with this then unpublished piece. A likely explanation is that both composers took the theme from another unknown source.