This thesis examines organ reform in England between 1901 and 1965, an arena of practical music-making and intellectual and ideological debates in which a number of related practices surrounding the English organ – notably its scholarship, aesthetics of design, liturgical functions, native and foreign repertoires, including J. S. Bach’s organ music – played a central role in transforming the sound, design, and appearance of the instrument. Whilst influential musicians asserted that the English organ of the first half of the twentieth century was a great work of art, and survived in what could be termed ‘splendid isolation’ from Continental models, others contended that it lacked a logical relationship with more than a home-grown repertory. However, supporters of the English organ claimed that technological and tonal improvements made it the most perfect medium for Bach performance. It was a renewed interest in historical organs and repertory that exposed the limitations of cultural centrism, pointing to the English organ’s weakness as a point of departure for understanding its European repertory. This insistence paved the way for an enthusiastic reception of other organs, which, through their construction and new tonal qualities, won the favour of musicians who had found the English organ too limited and focused on a particular culture. The thesis allows historical actors to populate the discourse, revealing the diverse practices out of which a quest for reform emerged. As such the organ provides a fascinating and preliminary rehearsal case for what in the 1970s and 80s would be termed the early music revival.