materials, and the scattered additions to Nissen's collection which came in from time to time were but scanty gleanings; it was essential to reach the original sources. My journey to Vienna in 1852 was undertaken, as you know, chiefly with the object of collecting such traditions of Beethoven as might remain there; I did not hope to find much which might lead to a closer knowledge of Mozart. Living testimony as to his life, person, or circumstances was almost extinct, little of what I learnt was from impressions at first hand, and it was generally necessary to guard against such communications as the result of book knowledge distorted by verbal transmission. Nevertheless, my visit was an instructive one even as concerned Mozart. Widely different as was the Vienna of 1852 from the Vienna of 1780 to 1790, yet much was gained by actual observation and impressions, which could not be given by books, and which operates more in the colour and tone of the whole representation that in any precise details. Intercourse, also, with accomplished friends led to much which would otherwise have remained untouched. My valued friend Karajan in particular, with his musical knowledge and his intimate acquaintance with Vienna, rendered my stay in that city as instructive as it was agreeable. He had a good opportunity of experiencing how much trouble one is capable of giving to a friend who is always ready with explanations, and willing to enter on the driest search into matters of detail, if he can thereby help forward another. At the Imperial Library I found not only the different manuscripts of the Requiem which serve as the surest testimony on the much debated question of its authorship, but many other important manuscripts and rich material of all kinds, my access to which I owe to the unfailing courtesy of the custodian, A. Schmid. But the most important aid came from Aloys Fuchs. With extraordinary perseverance he had collected every writing that in any way related to Mozart, and with a disinterested liberality, rare among collectors, he placed at my service all that he possessed and all that he knew. {INTRODUCTION.} (xv) His chronological catalogue of all Mozart's works, published and unpublished, was of the greatest service to me, as well as the long list of documents, newspapers, journals, and pamphlets, which he had either in the original or copies.