The following methods, though out of print, contain useful insights into accompanying and used copies may be purchased online.
Bridge, J. Frederick. Organ Accompaniment of the Choral Service. London: Novello and Co., 1885.
Buck, Dudley. Illustrations in Choir Accompaniment with Hints in Registration: A Hand-Book. New York: G. Schirmer, 1888.
Coleman, Henry. The Church Organist. London: Oxford University Press, 1955.
Conway, Marmaduke P. Church Organ Accompaniment. London: The Canterbury Press, 1952.
Demarest, Clifford. Hints on Organ Accompaniment. New York: The H.W. Gray Company, 1910.
Grace, Harvey. The Complete Organist. London: Grant Richards Ltd., 1920.
Richards, H.W. The Organ Accompaniment of the Church Services: A Practical Guide for the Student. Boston: The Boston Music Co., 1911.
Richardson, A. Madeley. Modern Organ Accompaniment. London: Longmans, Green, and Co., 1907.
Whiting, Geo. E. Organ Accompaniment and Extempore Playing. Boston: New England Conservatory of Music, 1887.