Mozart was busily employed in arranging his opera for harmony (wind) music, when he received a commission from the Haffner family in Salzburg (Vol. I., p. 153) to compose a new serenata. L. Mozart had first been applied to, and he thought it becoming that Wolfgang should lighten his father's labours by undertaking a work which cost him no exertion, and would be of direct advantage to his father. He therefore begged him to write a serenata without delay, for the time was approaching when it was to be performed. Wolfgang was quite ready to consent, inconvenient as it might be to him (July 20, 1782):-- I have certainly enough to do, for by Sunday week my opera must be arranged for wind instruments, or some one else will get the start of me, and reap the profit; and now I have to write a new symphony! I hardly see how it will be possible. You would not believe how difficult it is to arrange a work like this for harmony, so that it may preserve its effects, and yet be suitable for wind instruments. Well, I must give up my nights to it, for it cannot be done any other way; and to you, my dear father, they shall be devoted. You shall certainly receive something every post-day, and I will work as quickly as I can, and as well as I can compatibly with such haste. {HAFFNER--SERENATA, 1782.} (211) He kept his word, although not quite so soon as he himself wished. In his next letter he writes (July 27, 1782):-- You will make a wry face when you see only the first allegro; but it could not be helped, for I was called upon to compose a serenade in great haste--but only for wind instruments, or else I could have used it for you. On Wednesday, the 31st, I will send the two minuets, the andante, and the last movement: if I can I will send a march also; if not, you must take that belonging to the Haffner music, which is very little known (249 K.). I have written it in D, because you prefer it. But the serenata was not ready within the next few days, for he says in his letter of July 31:-- You see that my will is good, but if one cannot do a thing--why one cannot! I cannot slur over anything, so it will be next post-day before I can send you the whole symphony. A week later he wrote (August 7, 1782):-- Herewith I send you a short march (probably 445 K.). I hope all will arrive in good time, and that you will find it to your taste. The first allegro must be fiery, and the last as quick as possible.