John Julian, M.A., vicar of Wincobank, Sheffield
Wikipedia pretty well sums it up at http://en.wikipedia.org/wiki/A_Dictionary_of_Hymnology:
A Dictionary of Hymnology: Origin and History of Christian Hymns and Hymnwriters of All Ages and Nations, Together with Biographical and Critical Notices of Their Authors and Translators by John D. Julian, first published in 1892, is a standard historical reference for early Christian hymns, with more than 40,000 entries.Has the limitations -- and strengths -- of its era. I haven't seen anything else with Julian's level of detail about some of the chorales I've looked at. Has a detailed analysis of the Bay Psalm Book, too.
The work contains biographical and historical notes about the history of hymns and hymn writers. It is not a collection of hymn texts or hymn tunes, though brief quotations and references are included. Originally published in 1892 in London by John Murray and in New York by Charles Scribner's Sons, it was reprinted in 1907-1908 by John Murray, in 1957 by Dover Publications (in two volumes) and in 1985 by Kregel Publications. It was not revised after 1902, but remains an important source for early Christian hymns, such as Latin ones.
Screen grab of Liebster Jesu wir sind hier Deinem Worte nachzuleben is pretty typical of its depth of coverage (click to enlarge)
Hymnal for churches and Sunday-schools of the Augustana Synod. (1899) http://archive.org/details/hymnalforchurche00evan
Author: Evangelical Lutheran Augustana Synod of North America.
Subject: Evangelical Lutheran Augustana Synod of North America; Lutheran Church; Sunday schools; Hymns, English
Publisher: Rock Island, Ill. : Lutheran Augustana Book Concern
Call number: SCB
Digitizing sponsor: Calvin College
Book contributor: Princeton Theological Seminary Library