Guido d\'Arezzo

Arezzo, Guido d' [Guy of Arezzo] (b. 990s, d. after 1033)
Guido was a Benedictine monk and music educationalist from Northern Italy. When Guido was in his mid-30s, he compiled a manual entitled Micrologus ('Short Treatise'), which became the most widely transmitted musical pedagogical text of the medieval era. Micrologus presented a method whereby young people could accurately learn plainchant melodies using a monochord. Later, Guido described staff notation (in a Prologue to a now lost antiphoner). And in his Epistola ('Letter') to Brother Michael in Pomposa, near Ferrara, Guido explained how to derive solmization syllables (ut, re, mi, fa, sol, la) from the plainchant hymn 'Ut queant laxis'. Guido recommended that musical notation should not use a staircase staff (where successive lines represent diatonic steps), but a ladder staff instead (where lines represent pitches a third apart). Guido also pioneered the use of clefs and coloured lines (yellow for c', red for f) as an elegant way of indicating where semitones occur within the stave.
Guido was opinionated and outspoken, and consequently he was ostracized by the other monks at the monastery in Pomposa. What irked Guido's colleagues was that by providing a method whereby even young people could teach themselves how to sight-sing plainchant melodies, educational control was wrested from the monks. Guido's unpopularity prompted his move to Arezzo, where the Bishop arranged for Guido to train the cathedral's singers. Micrologus followed in 1025 or 1026. Although the celebrated Guidonian Hand was an elaboration of Guido's innovations, the fully-fledged hexachordal system was not Guido's own. But Guido's pioneering use of staff notation, his belief in the benefit of developing pitch memory, and his promotion of a direct correspondence between graphic notation and vocalized sound, make Guido a founding father of Western classical music's sight-reading culture and its reliance on the musical score.
Further reading:
W. Babb & C. Palisca (eds) Hucbald, Guido, and John on Music: Three Medieval Treatises Music Theory Translation Series, 3 (New Haven: Yale University Press, 1978)
S. Mengozzi The Renaissance Reform of Medieval Music Theory: Guido of Arezzo between Myth and History (Cambridge: Cambridge University Press, 2010)
D. Pesce (ed. & trans.) Guido d'Arezzo's Regule Rithmice, Prologus in Antiphonarium, and Epistola ad Michahelem: a Critical Text and Translation with an Introduction, Annotations, Indices, and New Manuscript Inventories (Ottawa: Institute of Mediaeval Music, 1999)

Jeremy Summerly