This work was made possible through the purchase by the Sibley Music Library, Eastman School of Music, University of Rochester, in 1929 of an eleventh century codex containing, among other treatises, the Musica of Hermannus Contractus. This was not available when Gerbert and Brambach made their editions which are based entirely on the Vienna codex #51.

The Vienna National Library, through its director, Dr. Josef Bick, was so courteous as to furnish us with a photostatic copy of the latter, thus making both MSS., the only ones known to contain the Musica, available for collation in this present edition.

The reader will note that while in general the two MSS. are consistent, in several significant places the Rochester codex has cleared up impossible grammar and juggled terms which are found in the earlier editions.

The writer has been deeply indebted to his adviser, Dr. Charles Warren Fox, many times in the course of this work for patient council and thorough guidance, also to Mr. Gomer Ll. Jones for his extensive collaboration in connection with the translation of the Musica. He is grateful, too, for the helpful suggestions he has received from Professor Harry Caplan of Cornell University and Dr. Ruth Hannas.