This dissertation considers the history of the organs in Westminster Abbey and the music performed on them from the eleventh century to the start of the twentieth. It is primarily based on the documentary evidence in Westminster Abbey Library and Muniment Room and transcriptions of material from here form a large part of the appendices. The thesis considers the organs built especially for the Abbey and temporary instruments used for coronations and other events. The organ builders represented include John Howe, Thomas Dallam, John Burwood, Bernard Smith, Christopher Shrider, Thomas Elliot and William Hill. The organists of Westminster Abbey include the composers Edmund Hooper, Orlando Gibbons, John Blow, Henry Purcell, William Croft, Benjamin Cooke and James Turle. Compositions they wrote while in post are used as sources of information about the organ, and are related to the details of the instrument found in documentary and secondary sources. The compositions are used to evaluate these details when appropriate. A new edition of Benjamin Cooke's organ voluntaries and his Magnificat and Nunc Dimittis in G form part of the dissertation. The voluntaries appear together here for the first time in a modern edition. The choral repertoire is discussed with reference to part books used in the Abbey from the Restoration until the beginning of the twentieth century and to a catalogue of printed music in the choir library compiled around 1905. The role of the organ in the liturgical life of the Abbey is considered, and the political events which affected this are introduced and discussed. Coronation services take place in the Abbey. The music performed at these from Charles II to Victoria is established as far as possible from service books in Lambeth Palace Library and other sources. The musical forces available at coronations are discussed, including organs built in the Abbey especially for these events