A writer on musical history must above all be a musician of practical experience--an accomplished executant on at least one instrument, so that he is enabled to familiarize himself with the compositions of different masters more thoroughly than could otherwise be possible; and a composer in order to form a correct judgment of the compositions of others. The opinion about Handel or Bach of a writer who is but imperfectly practised in counterpoint, and who is incompetent to produce correctly a fugue or other intricate composition constructed according to fixed rules, is not likely to prove of use to the student of musical history. Burney possessed many of the qualities requisite for a musical historian. He was a professional musician systematically trained in the art, and an intelligent inquirer without pedantry or prejudice. Moreover, he had the moral courage to rescind an opinion when he discovered that it was erroneous. For instance, respecting an opinion which he formerly held on German music, he candidly avows ('History of Music' Vol. IV., p. 606), "It was inconsiderately inserted in the first edition of my 'German Tour' before I was able to examine the truth.... So far, therefore from letting a second-hand prejudice warp my judgment, or influence my opinions in writing my General History, I have long been keeping double guard over my pen and my principles." The most valuable literary productions are generally to be found among the investigations which are confined to a certain branch of the art. The works which pretend to embrace its whole science are often but mere compilations by writers who, like Bottom the weaver, want to act not only Pyramus, but at the same time also Thisbe and the lion.[42] With the objectionable curiosities in musical literature might also be classed certain compilations which contain acute observations interspersed with silly remarks. In the preface the author states that he considers it an agreeable duty to acknowledge his obligations to other writers; but, as he does not indicate in the course of the book the sources from which he has drawn, most readers remain ignorant of the fact that the acute observations ought properly to have been given in inverted commas. Equally objectionable are certain productions bearing on the Êsthetics of music, in which the author shows with high-flown words that he is himself not quite clear about what he propounds. It certainly seems odd that just such worthless productions are often prefaced with the remark that the subject of the book has never been properly treated before, whereas there are generally much better works on the same subject well known to musicians.