What might have occasioned Mozart to rework his original Serenade for sextet into a version for octet (with two oboes) only a few months after he had completed it? Was there an ''external'' cause? Once Joseph II had founded an ''imperial wind ensemble'' in April 1782, octet music was in great demand. The ensemble with two oboes, two clarinets, two horns and two bassoons had to play on all manner of occasions. As we can gather from one of Mozart's letters, he therefore conjured up a ''Night Musique'' within a very short period of time. It is very probable that it was this arrangement.?