Book excerpt: Bach's organ works--the best-known of all music ever written for the instrument--have been the subject of a great variety of interpretations, all too often based on subjective opinion and conjecture. What the author does in this piece-by-piece commentary is to combine a performer's insight and experience with the fruits of scholarly research. He is concerned throughout to reconstruct for the modern performer and listener the original context of the work: its sources and history; its place in the composer's development; the implications of contemporary instruments and performing practice, and of the musical and aesthetic theories of the time; and the background which shaped Bach's view of the original chorale melodies. Each of the collections of organ chorales is examined as an entity in a preliminary essay. Then for each piece the author discusses the important sources and their relationship; quotes the underlying chorale melody and one or more verses of the text (with a literal translation) and describes its importance in the life of Bach's church; and analyses the form and style of the organ setting, with many musical examples and frequent allusions to the views of other commentators.