Listed below are various method books on the study of improvisation. Many are available through Amazon.com. Links to Amazon.com below are affiliate links and will result in a modest commission paid to me without any increase to your cost.
Jan Bender
Organ Improvisation for Beginners: A Book of Self-Instruction for Church Musicians : Op. 59
See a full review here.
Jeffrey Brillhart
Breaking Free: Finding a Personal Voice for Improvisation through 20th Century French Improvisation Techniques. Published by Wayne Leupold Editions.
See a full review here.
Michael Burkhardt
Creative Hymn Playing: Improvisation, Exercises, and Repertoire
See a full review here.
Francis Chapelet
Livre d’improvisation et d’accompagnement, éditions Les presses de la Double, 2002, 68 pages.
James Hannon Conely. A Guide to Improvisation: An Introductory Handbook for Church Organists. Nashville: Abingdon Press, 1975.
Marcel Dupré
Cours Complet D’improvisation a L’orgue/vol 1: French and English
Cours Complet D’improvisation a L’orgue/vol 2 English
Manuel d’Accompagnement du Plain-chant Grégorien
Petr Eben. Protestant Chorales from the Canzional of the Bohemian Brothers: Choral Variations and Improvisation Model. Wien: Universal Edition, 2002.
Peter Ewers
Just play! An invitation to improvisation
See a complete review of the book here.
Richard Grayson offers an improvisation handbook for free download on his website here.
Naji Hakim
The Improvisation Companion
United Music Publishers Ltd.
See a complete review of the book here.
Gerre Hancock
Improvising: How to Master the Art
Oxford University Press
See a complete review of this book here.
Reginald Hunt
Extemporization for Music Students
Oxford University Press
Michele Johns
Hymn Improvisation
Minneapolis, MN: Augsburg Publishing House, 1987.
Gerhard Krapf.
Organ Improvisation (A Practical Approach to Chorale Elaborations For The Service)
Minneapolis, MN: Augsburg Publishing House, 1967.
Musical Accompaniment of Moving Pictures
A Practical Manual for Pianists and Organists, and an Exposition of the Principles Underlying the Musical Interpretation of Moving Pictures
by Edith Lang and George West
Available through Amazon or for free at archive.org.
Robert C. Lau
A Practical Approach to Improvisation for the Church Organist
Paraclete Press
Hamilton Crawford Macdougall
First lessons in Extemporizing on the Organ
Available for purchase from Amazon or as a free download from archive.org.
See a brief review of the book here.
Jan Overduin
Making Music: Improvisation for Organists
Jan Overduin provides a method to enable the student to improvise from the beginning of keyboard study. See a complete review of this book here.
The Haarlem Essays
Edited by Paul Peeters
published by J. Butz Verlag (Bonn)
ISBN 978-3-928412-15-5
Available through OHS.
Modulation
Composer Max Reger offers a guide on how to modulate from one key to another. He provides different progressions for enharmonic key relations creating 46 potential modulation progressions from a major key and 54 progressions from a minor key. If you don’t know how to get from one key to another, this is the place to look.
Alfred Madeley Richardson
Extempore Playing: Forty Lessons in the Art of Keyboard Composing
Available in print from Amazon or for free from archive.org
Lionel Rogg has written an Improvisation Course for organists, published in French and English by Editions Musicales de la Schola Cantorum. Volume 1 is practical harmony, ornamental counterpoint and chorale. Volume 2 is modal and free styles.
See a complete review of volume one here.
Rotermund, Donald
Off the Page, Tips & Techniques for Creating Hymn-Based Organ Settings
Off the Page, Too: Tips and Techniques
Two volumes with instructions to create a variety of pleasant settings based on the notes of the hymnal harmonizations. The hymnal serves as the basic printed resource for taking something “off the page.” Each self-directed chapter treats a different technique, and it’s not necessary to work through the chapters in order.
Pamela Ruiter-Feenstra
Bach and the Art of Improvisation
Ann Arbor, MI: CHI Press, 2011.
See a complete review of this book here.
Frank J. Sawyer
Extemporization
Hennie Schouten
Improvisation On The Organ
This is a reprint edition of a book originally published prior to 1923. It is an English translation by J. L. Warren of the original Improviseren op het Orgel in Dutch. The book is aimed primarily at church organists wishing to improvise chorale preludes. It covers both homophonic and polyphonic improvisation styles and expects the reader to have a foundation in harmony and theory before beginning.
Franz Josef Stoiber
Gehörbildung, Tonsatz, Improvisation
This book is in German.
Charles Tournemire
Précis d’éxecution de registration et d’improvisation à l’orgue
Published by Éditions Max Eschig in 1936. Of the 117 pages, only the last 16 are devoted explicitly to the art of improvisation. Much of the text is devoted to philosophy, references to examples in repertoire, with some explanation of forms. Tournemire writes that the most profitable study that one could do is to read each day a sonata of Haydn, Mozart or Beethoven, and then to take the same elements and try to develop them oneself.
Sietze de Vries
Harmonizing: A Method to Encourage the Art of Improvising.
This book covers basic theory while gradually moving toward improvising using I, IV, and V in easier keys. As the book advances, he includes harmonizing and improvisation on ii, iii, and vi as well as in minor keys and even church modes. Published by Boeijenga Music Publications. Available from the OHS Catalog here.
George E. Whiting
Organ Accompaniment and Extempore Playing
Available for free at IMSLP. Reviewed in Newsletter #41 – How’s the weather?
T. Carl Whitmer
The Art Of Improvisation
A Handbook of Principles and Methods for Organists, Pianists, Teachers and All Who Desire to Develop Extempore Playing, Based Upon Melodic Approach
Available in paperback at amazon.com