A monk of the Order of St. Benedict, b. (according to Dom Morin in the "Revue de l'art Chretien", 1888, iii) near Paris c. 995; d. at Avellano, near Arezzo, 1050. He invented the system of staff-notation still in use, and rendered various other services to the progress of musical art and science. He was educated by and became a member of the Benedictine Order in the monastery of St. Maur des Fosses, near Paris. Early in his career Guido observed the confusion which prevailed in the teaching and performance of liturgical melodies generally, and especially in his immediate surroundings. His endeavours to improve these conditions by innovations in the current methods of teaching are fully described in his writings; these made him unpopular with his brethren in the order and led to his removals to the monastery of Pomposa near Ferrara, Italy. Here the same lot seems to have befallen him. Intrigues and calumnies caused him to ask for admission to the monastery of Arezzo. The exact date of his entrance into this community is uncertain, but it occurred during the incumbency of Theudald as Bishop of Arezzo (i.e., between 1033 and 1036), and while Grunwald was abbot of the monastery. It was during this period that Guido perfected the new system of notation which brought such order and clearness into the teaching of music. Guido seems by this time to have overcome all opposition to his new method, and to have removed all doubt as to its value among those who took cognizance of it and saw its application. His fame soon reached the reigning pope, John XIX (1024-1033), who sent three different messengers urging Guido to come to Rome and exhibit his antiphonary containing the liturgical melodies transcribed from the sign-notation heretofore in use into his own staff-notation. Pope John was overjoyed at the ease with which he was enabled to decipher and learn the melodies without the aid of a master, and invited Guido to take up his abode in Rome, to instruct the Roman clergy in the new system, and to introduce it into general practice in the Eternal City. Unfortunately the Roman climate made it impossible for Guido to accept the invitation of the supreme pontiff. He soon fell ill of Roman fever and had to leave the city. He now returned to the monastery of Pomposa. The abbot (also called Guido) and monks, who had caused him so much chagrin by their opposition to his innovations, now received him with open arms, admitted their former mistake, and urged him to become a member of the community. His stay at Pomposa seems to have been only of short duration, for he soon returned to Arezzo. Regarding the remaining days of the reformer, traditional reports vary. M. Faulty (Studi su Guido Monaco, 1882) holds that Guido ended his days at Arezzo, while others are of the opinion, based upon the chronicle and other evidences of a Camaldolese monastery near Avellano, that Guido died there as prior in the year 1050. Guido himself has left to posterity in his "Epistola Michaeli monaco Pomposiano" (reprinted in Gerbert's Scriptures, ii) a naive but lively description of his, for the most part, eventful life, its trials and bitterness, and his final triumph over the opponents of his innovations.

In order to realize the importance of Guido's services to musical progress and development it is necessary to take a glance at the systems of the notation in use before his time. Since in the early Church the liturgical melodies were not very numerous and were in daily use, they were easily perpetuated by oral transmission among the clergy, the chanters, and the people; but, as Christian hymnody developed with the expansion of the liturgy, and as the number of feasts increased the melodies became too numerous to be learned and retained by the memory without the aid of some unchangeable means. The absence of this determining means, the frequent carelessness of copyists, the temperament and even caprice of singers, and the great variety of conditions under which they were propagated and performed caused the melodies to undergo numerous changes. The necessity for a system of notation which would clearly record the various intervals of the melodies became more and more urgent. While in theoretical treatises the practice of the Greeks of employing the first fifteen letters of the alphabet to designate the various intervals was still in use, there was no means at hand by which the intervals and rhythm of a melody ;might be graphically displayed, so that anyone might learn it from a manuscript without the aid of a master. The so-called neumatic notation (from meuma, a nod), which probably in the eighth century found its way from the Orient into the Latin Church, where it suffered many modifications, had mainly a rhythmical purpose, and was intended to serve only in a general way a diastematic end, i.e. an indication of the intervals of the melody. An attempt to indicate the intervals with greater precision was made by placing the neumatic signs at a lesser or greater distance from the words comprising the text, and, in order to obtain more exact results from this proceeding, the copyist would draw a line upon which he would place one of the letters of the alphabet and from which he would measure the distance of the melodic steps above or below. It is held that Guido found two such lines in use, namely, a red one upon which F was placed, and a yellow one for C, indicating the place of the tones represented by these letters of the alphabet and employed by theorists of his time. His great improvement consisted in adding two more lines to the existing ones, in utilizing the spaces between the lines themselves and in indicating, by combining the letters of the alphabet with the neumatic signs, not only the various intervals of the melody, but also its rhythm. This system, called staff-notation, has been used ever since. The reason why only four lines were used, instead of the five we employ, is that these four and the five spaces were regarded as sufficient for the ambitus, or range, of the average Gregorian melody. In the course of time as the melodies were transcribed into the new notation, the neumatic signs formerly in use evolved into our present notes, and the letters F and C became the clefs of later times. Guido's influence was so great in his time that many things have been attributed to him which belong to a later period; but which are elaborations and developments of his teachings. The impetus he gave to musical progress lasted throughout the Middle Ages. Especially did incipient polyphony advance by his advocacy of contrary motion of the voices as against the still prevailing parallelism. Of the works attributed to him, the following are undoubtedly authentic: "Micrologus de disciplina artis musicae', which treatise, especially the fifteenth chapter, is invaluable to present-day students endeavoring to ascertain the original rhythmical and melodic form of the Gregorian chant; "Regulae de ignoto cantu", prologue to his antiphonarium in staff-notation; "Epistola Michaeli monaco de ignoto cantu directa:. All these were reproduced in Gerbert's "Scriptores", ii, 2-50.

Falchi, Studi su Guido monaco (1882); Les melodies gregoriennes d'apres la tradition (Tournai, 1880); Ambros, Geschichie der Musik, II (Leipzig, 1880), 144-216; Riemann, Handbuch der Musikgeschichte, I (Leipzig, 1905), ii.

JOSEPH OTTEN