This Companion is an essential guide to all aspects of the organ and its music. The early chapters examine the instrument's history and construction, and consider the scientific basis of its sounds, pitch and tuning. Central chapters investigate the practical art of learning and playing, and introduce the complex area of performance practice, while the final section explores the vast repertoire of organ music, by country, focusing on a selection of the most important traditions. The contributors are all experts in their field, making this the most authoritative reference book currently available.