The Creative Use of the Organ In Worship by Hal H. Hopson. For Solo Organ. Collection. Creative Use Series. Sacred, General. Moderate. Organ Book. Published by Hope Publishing Company (HP.8070).
An extensive resource of 250+ hymn reharmonizations, plus 21 ways to improvise hymntunes for use as service music, along with a complete listing of modulations and 5 harmonizations for The Doxology.