Since we are now in the thick of the Midsummer Mozart Festival, I find myself both playing and listening to more Mozart at home; and this has set me to visit some old speculations. About 35 years ago, when I was teaching at the University of Pennsylvania, I had a British colleague whose used to talk with delight about a friend of his who had begun a piano recital with the first entry in Ludwig von Köchel's chronological catalog of the compositions of Wolfgang Amadeus Mozart. Many years later I bought myself a copy of the Henle edition of Mozart's Klavierstücke, edited by B. A. Wallner and apparently completed in the spring of 1974 (quite possibly around the time that my colleague told me his story). When I turned to the first page of music, I encountered the same anomaly that confronted me with two of the works on the first Midsummer Mozart Festival program this season, the dreaded parenthesis that follows the K number in the listing "KV 1 (1e)."
Now that it is easier to come by resources to deal with such puzzles, I decided it was finally time to address it. Naturally, I began my efforts with the digitized version of the Neue Mozart-Ausgabe, whose entry for K. 1 basically aligned with my Henle edition with only a minor discrepancy. The entry was published as a minuet with a trio but with the editor's comment that these may have been "two independent minuets." The Neue Mozart-Ausgabe bundles these options together with the listing "Menuett in C KV 1, Trio (KV6 1f)." (That superscript "6" refers to the sixth edition of the Köchel catalog, completed in 1964, while the absence of a superscript indicates the original catalog of 1862.)
Next, I decided to consult the notes from my Brilliant Classics collection of the complete works of Mozart. For this particular collection of keyboard music, the notes were by Jérôme Lejeune. Since the CD in the Brilliant collection included the four entries from KV6 that did not show up in the original catalog, I was hoping that Lejeune would offer some insights; and I was not disappointed. Here is Lejeune's account of the complete set:
These pieces probably have their origin in the Nannerl Notenbuch; Leopold Mozart had given Nannerl [Mozart's sister, with whom he played his later concerto for two pianos] a rectangular music-book in 1759 into which he had carefully written onto the title-page “Pour le clavecin. Ce livre appartient à Mademoiselle Marianne Mozart”, taking care to copy works of increasing difficulty by various fashionable composers into it. When Wolfgang later came to play these pieces at the age of 4, Leopold marked down the date on which he first saw them. Leopold also transcribed the first pieces that young Wolfgang wrote into this same book.
The Neue Mozart-Ausgabe lists 52 entries in this notebook, followed by twelve additional entries, apparently from the "original" (ursprünglich) version of the notebook; and all six K.1 entries are among those twelve additional pieces. There is no immediate indication of which of those entries were initially in Wolfgang's hand; but Lejeune's comment about Leopold's transcription would explain why the notebook has two versions. If I want to pursue further details, I shall probably have to follow up on the footnotes to the editorial comments in the Neue Mozart-Ausgabe, which will require more attention to wading through musicological German than I can muster on a Sunday morning!