"Some years since, the renowned French theorist, Mons. Fetis, went to
Milan for the express purpose of consulting the celebrated _Book of
Offices_, written by St. Ambrose _in his own handwriting, which is
there preserved_ [the Italics are added]; and in his work, published in
Belgium, he says that he collated them with those known and received
amongst us; and that the variations were of the slightest possible
character, the tones being ostensibly the same."
This extraordinary statement cannot be accepted without the title of M.
Fetis' work, and the passage upon which it rests, _verbatim_ in the
author's own words. But I have no hesitation in saying that it is founded
in error.
Thibaut (_Ueber der Reinheit der Tonkunst_, pp. 28-30.) speaks of a MS. of
the Gregorian chants at St. Gall, in Switzerland, as old as the _ninth_
century. This is believed, by all accredited modern writers upon music, to
be the oldest MS. of the tones extant.