Linked from
The 10 pages that link to Guido of Arezzo, each with the reason it gives.
Musical notationRelated: His teaching methods helped make written pitches easier to identify.
MelismaRelated: His reforms helped transmit chant melodies, including their melismatic passages.
NeumeRelated: His staff-based innovations made pitch relationships easier to learn and record.
Sheet musicRelated: His teaching methods helped make written pitch relationships easier to learn.
ClefRelated: His staff innovations helped make fixed pitch references useful in written music.