in corroboration of my statements. A reference to the number in Köchel's catalogue became, in most cases, sufficient; and I was able also to omit notices of errors in the published works which Köchel had remarked upon. These, as far as the great operas are concerned, will soon be rendered still more superfluous by the projected new edition of the scores from the autograph originals. Köche's friendship, which I regard as the greatest gain of our common labours, has aided and supported me throughout the preparation of this edition. I will not attempt to enumerate all that he has communicated, verified, and brought into agreement for me: he knows the amount of his aid and of my gratitude. Sonnleithner, Karajan, Pohl, Jul. André, have been equally obliging in satisfying my demands and inquiries. Special thanks are due to them if my book attains that accuracy of detail, wherein I place its chief value. I may claim to have made tolerably exhaustive use of all that has been published concerning Mozart during the last ten years, but you will scarcely expect me to enumerate all my corrections and improvements. It has been my aim to retain all that had been proved good in my work, while making such additions as served to place my subject more clearly and fully before my readers. If a perusal of my second edition should leave you with the impression that the task of revision and correction has been an easy one, I shall, whatever my convictions to the contrary, congratulate myself on having approached the object which I have kept steadily in view. Accept my book, then, in its new dress, with the old spirit of friendship, and gladden the heart of its author once more by the sympathy he has never yet found wanting. OTTO JAHN. Bonn, March 6, 1867. TRANSLATOR'S NOTE. CONSIDERABLE doubt has existed in the mind of the translator as to the proper English equivalent for the word "clavier" throughout this work. Clavier is a generic term in German, and is used to denote any keyed instrument, whether harpsichord, clavichord, or pianoforte. Mozart's compositions for the clavier are equally available for all these instruments, and in his early years he performed indifferently on the harpsichord or clavichord. His first introduction to the pianoforte was at Augsburg, in 1777, and he did not become familiar with the instrument until after his settlement in Vienna in 1781. It has been thought best, therefore, to leave the word _clavier_ untranslated up to this date, after which it is translated _pianoforte_, whether it is applied to Mozart's performances or to his compositions.