The documents discovered by Dom Germain Morin, the Belgian Benedictine, about 1888, point to the conclusion that Guido was a Frenchman and lived from his youth upwards in the Benedictine monastery of St Maur des Fosses where he invented his novel system of notation and taught the brothers to sing by it. In codex 763 of the British Museum the composer of the "Micrologus" and other works by Guido of Arezzo is always described as Guido de Sancto Mauro. There is no doubt that Guido's method shows considerable progress in the evolution of modern notation. It was he who for the first time systematically used the lines of the staff, and the intervals or _spatia_ between them. There is also little doubt that the names of the first six notes of the scale, _ut_, _re_, _mi_, _fa_, _sol_, _la_, still in use among Romance nations, were introduced by Guido, although he seems to have used them in a relative rather than in an absolute sense. It is well known that these words are the first syllables of six lines of a hymn addressed to St John the Baptist, which may be given here:-- _Ut_ queant laxis _re_sonare fibris _Mi_ra gestorum _fa_muli tuorum, _Sol_ve polluti _la_bii reatum, Sancte Joannes. In addition to this Guido is generally credited with the introduction of the F clef. But more important than all this, perhaps, is the thoroughly practical tone which Guido assumes in his theoretical writings, and which differs greatly from the clumsy scholasticism of his contemporaries and predecessors. The most important of Guido's treatises, and those which are generally acknowledged to be authentic, are _Micrologus Guidonis de disciplina artis musicae_, dedicated to Bishop Theodald of Arezzo, and comprising a complete theory of music, in 20 chapters; _Musicae Guidonis regulae rhythmicae in antiphonarii sui prologum prolatae_, written in trochaic decasyllabics of anything but classical structure; _Aliae Guidonis regulae de ignoto cantu, identidem in antiphonarii sui prologum prolatae_; and the _Epistola Guidonis Michaeli monacho de ignoto cantu_, already referred to. These are published in the second volume of Gerbert's _Scriptores ecclesiastici de musica sacra_. A very important manuscript unknown to Gerbert (the _Codex bibliothecae Uticensis_, in the Paris library) contains, besides minor treatises, an antiphonarium and gradual undoubtedly belonging to Guido. See also L. Angeloni, _G. d'Arezzo_ (1811); Kiesewetter, _Guido von Arezzo_ (1840); Kornmuller, "Leben und Werken Guidos von Arezzo," in Habert's _Jahrb._ (1876); Antonio Brandi, _G. Aretino_ (1882); G. B. Ristori, _Biografia di Guido monaco d'Arezzo_ (1868).