The mystery of Mozart's compositional method

We don't know much of how Mozart composed, whether he really did all the work in his head and wrote the fair copy down immediately, or went through drafts which then got destroyed. We have Beethoven's sketchbooks for evidence that he did a lot of rewriting, and Brahms admitted that he burnt most of his attempts to write a string quartet - not to mention agonizing for a decade or so over his first symphony. Haydn's method of musical composition is more mysterious: the large number of pieces that he completed points to a fairly rapid and efficient method, but he probably used sketches and tried things out at the piano. But lack of surviving sketches is no evidence that sketches never existed. The document "'A Letter' from Wolfgang Amadeus Mozart", and the great speed with which he composed, reinforce the belief that he conceived everything fully-formed in his head, but the authenticity of the letter is doubtful.

In the dedicatory letter to Joseph Haydn that accompanied a set of six string quartets, Mozart said that they had cost him much trouble to compose. To quote John Sichel's Program Notes,

"Mozart called the quartets the result of 'long and arduous labor' and so they were, especially for this phenomenon of nature from whom music usually flowed like water from an open fire hydrant. He wrote the six quartets over the course of three years (by comparison he wrote The Marriage of Figaro and his great C minor piano concerto K. 491 in two months) and the number of false starts, erasures and alterations in the score bespeak the effort and care involved."
By contrast, the Trio K. 498 for clarinet, viola and piano was reputedly written in a bowling alley at a single sitting, leading to the name "Kegelstatt". However as with many stories about Mozart, this is disputed, for example by Stanley Geidel:
'Plath and Rehm point out that the subtitle "Kegelstatt" was possibly erroneously transferred from Mozart's set of Twelve Duos for Two Wind Instruments, K. 487. The manuscript of these Duos, dated nine days earlier than the Trio, bears the inscription "untern kegelscheiben" (i.e., "during a game of skittles"). Kochel, in his catalog of Mozart's work, confirms this inscription in the Duos. No similar inscription appears in the manuscript of the Trio.

I have personally examined the manuscript of the Trio at great length, and written extensively on this great work. It is very clear that the "Kegelstatt" music is in fact the Twelve Duos, this fact confirmed by a note in Mozart's own hand, which appears on the Duos. In the final analysis, all of this confusion most likely arose from a publisher's error.'

Geidel's thesis is strengthened by the relative length and importance of the two works - the Trio a substantial and involved masterpiece, the Duos, as far as I know, short and purely recreational.

Mozart was a complete musical professional, in addition to being a genius: growing up in a professional musician's household, he was perfectly at home with the formal and technical aspects of composition from his earliest years, so it is not difficult to believe that many of his compositions, especially the shorter and lighter ones, were written down directly in their final form.

It is sobering to see that Mozart took about 200 compositions, and over a decade of work, before he wrote anything interesting (rather than simply stylish and correct) - and a further hundred or so before his percentage of masterpieces reached a creditable level. His maturity as a composer took place only after adolescence, with a few exceptions (the violin concertos, the "Jeunehomme" piano concerto). (Hans Keller made this point well.)

Contrast Mendelssohn, who was original and interesting at 14 and could write profound masterpieces from 16 onwards. It would be fascinating to know what Mozart himself thought of his transition from empty fluency to fluent genius. Was he was inspired to raise his game by contact with other masterpieces (Bach, Handel and Haydn) rather than the insipid trash that mostly passed for music in the 1770's - or was such contact just a helping hand towards a maturity that was arriving of its own accord?