Book excerpt: Johann Sebastian Bach used his own organ compositions when teaching his students. Seeking to understand and learn from Bach's organ pedagogy, many scholars have sought to establish a list of Bach's organ works according to difficulty. These arranged lists are briefly summarized in chapter two of the present thesis, and it is shown that none of them have sufficiently explained the rationale for deciding difficulty. Chapter three establishes and describes criteria according to which Bach's organ works can be analyzed. Chapter four demonstrates how these criteria are to be applied within a selected corpus of J.S. Bach's organ works, the Leipzig versions of the Great Eighteen Chorale Preludes. The criteria and resulting arrangement according to difficulty answer a problem within Bach scholarship by providing an objective standard by which teachers and students can select level-appropriate works for purposes of learning and performance.