That Mozart could be a sly fellow. Music poured out of the guy seemingly effortlessly -- legend has it that the Kegelstatt Trio was written out while Mozart was waiting his turn at skittles -- but maybe it wasn't as always as easy as that. And the man did have to make a living, after all.
Take, for example, the flute concerto in D. According to S. W. Bennett, on the liner notes to the LP The Virtuoso Oboe:
[T]he financially hard-pressed Mozart had an opportunity to earn some money by writing for the flute, an instrument he disliked. A Dutch patron of music and flautist, M. de Jean, commissioned in 1778 a group of flute works, which Mozart had to supply in a hurry. He brought forth three flute quartets and two flute concertos.You're in hurry, you have some distant patron, and you don't even like the flute. So what do you do?
Of the latter [that is, the concertos] the one in D is undoubtedly the C major oboe concerto transcribed. As "almost conclusive evidence" Alfred Einstein points to the fact that in its D major flute form, the violin parts of the concerto never go below A on the G-string, indicating that the whole work was simply transcribed a whole tone upwards.Heh. Hey, maybe he won't notice that his commissioned flute concerto is actually an oboe concerto redone to make it more flute-y. But alas, it seems that De Jean did actually notice -- per the infallible Wikipedia, De Jean didn't pay Mozart for the concerto.
An interesting historical twist is that the oboe concerto was lost for many years, and only the flute concerto was in the repertoire. People knew from writings that there was an oboe concerto, but there was no manuscript. But a dude named Paumgartner eventually pieced it together in the 1920s:
This oboe concerto was first published in its present form in 1948, the editors using old manuscript parts in the Mozarteum library at Salzburg, but the music has long been known as the Flute Concert in D major, with the same K. number.Kids, don't let this happen to you. If you plagiarize, even yourself, your rich patron will find out and will stop the check. And don't forget to make backup copies of your originals, just in case.