Mozart originally wrote this concerto for a clarinet with an extended lower range, compared to the conventional instrument. As early as 1802, published versions appeared with registral changes, which made the concerto playable on instruments without the extra keys. When producing an edition for the conventional clarinet there are two choices to be made about the ‘extra’ notes - is it better to maintain the musical line, and hence transpose whole phrases or passages up an octave, rather than sing...