A. B. Marx

Currently, our only data on Marx is that he had the title "Doctor," and a tune he harmonized appeared in Great Hymns of the Church Compiled by the Late Right Reverend John Freeman Young, edited by John Hopkins (New York: James Pott & Company, 1887). Possibly he is Adolph Bernhard Marx (1795-1866 [http://en.wikipedia.org/wiki/Adolf_Bernhard_Marx], but we have no confirmation of this.

http://www.hymntime.com/tch/bio/m/a/r/x/marx_ab.htm