From 1784 he kept his own catalogue: a date, a title, the opening bars, one entry per work. When we can say exactly what day a piece was finished, it is usually because that notebook survives.
Mozart was born in Salzburg in 1756. His father Leopold was a court musician and his only teacher. From the age of six Leopold took him and his sister touring across Europe for the better part of a decade — not an education but a job.
At twenty-five he fell out with the Archbishop of Salzburg and was thrown out, and from then on he lived in Vienna on his own account: teaching, running subscription concerts, taking commissions, selling scores. Almost nobody worked that way then; there was no salary, and the income rose and fell with the season and with fashion.
In 1784 he began the catalogue of his own works and kept it up until a month before he died. The summer of 1788 was one of his densest stretches: the last three symphonies were finished between June and August, and the entry for 26 June in that same book is a little piano sonata for beginners — K. 545.
He died in Vienna on 5 December 1791, aged thirty-five, at work on a Requiem commissioned anonymously and left unfinished.
He left more than six hundred works, and the ones most thumbed in piano rooms today are mostly the ones he tossed off for his own pupils.
Mozart's tunes are nearly always a question and an answer — four bars up, four bars down, square, memorable on one hearing. That is the easiest way to recognise him.
The accompaniment is usually a single unchanging action: a four-note circling figure (called an Alberti bass), or one chord struck again and again. Because the action never changes, the tune above it stays clear.
His harmony is clean and modulations rarely feel like being pulled anywhere; but he loves to go suddenly quiet at the end of a phrase, or to push the expected cadence back by a bar. That pause is usually the point of the whole sentence.
One more thing: almost everything he wrote can be sung. He wrote more than twenty operas, and the habit stayed in all his instrumental music.
