Originally published in 1967, in this book the author delves deeply into the fascinating field of Bach's music and the reasons for his 'borrowing', and adaptation within his oeuvre. This book, scrupulously uncontroversial in its manner, contains evidence which upends many established judgements. Whether concerned with Bach's artistic personality or with details of his performance, this voluminous record, with commentary, of his adaptations, recompositions or transcriptions is an essential work of reference. When it was first published much of the information on the Choralgesänge and the chorals contained in or intended for the Orgelbüchlein was available for the first time in English.