The British Museum has a virtual copy of Mozart’s Musical Diary and it’s fantastic!
This manuscript is Mozart’s record of his compositions in the last seven years of his life, and thus is a uniquely important document.
During this period, from February 1784 until December 1791, he composed many of his best-known works, including his five mature operas, several of his most beautiful piano sonatas, and his last three great symphonies, as well as several famous lesser works. It was a turbulent time of his life, with financial crises, family tragedy, and his ongoing unsuccessful search for a permanent court position.
Mozart organised the entries in the catalogue in the order in which they were completed. On the left-hand page he entered five compositions, each with its date, title, and often its instrumentation. He sometimes added further information such as the name of the singer, where it was composed, or who had commissioned the piece. He divided the right-hand page into five pairs of staves on which he wrote the opening bars of each work.
According to the description on the front cover, Mozart planned to include all his compositions, but there are a few minor omissions. Intriguingly, there are also entries in the catalogue for a number of works that have since been lost.
Mozart made his last entry in the catalogue just three weeks before his early death in December 1791. His last great work, a requiem, was not entered as it remained unfinished at his death.
British Library, Zweig MS 63
Check it out!
(I recommend using the SilverLight plugin)