Ryden, Ernest Edwin, The Story of Our Hymns. Augustana Book Concern, 1930.
Popular in style. Part III deals with Scandinavian hymnody. The author is a Lutheran hymnologist.
Schaff, Philip, Literature and Poetry. Scribner, 1890.
Contains an informative chapter on St. Bernard as a hymnist.
English Hymnody
Benson, Louis F., The English Hymn. Doran, 1915.
Best source of information on the development and use of standard English and American hymns. Scholarly. Unfortunately out of print.
Brawley, Benjamin, History of the English Hymn. Abingdon Press, 1932.
Popular in style.
Duffield, Samuel Willoughby, English Hymns. Funk and Wagnalls, 1886.