Guido d’Arezzo, also called Guido of Arezzo, was born in Italy in the year of 990 and he died in 1050 in Avellana . He was a music theorist whose ideas and theories are the foundation modern western music notation. He was educated in Pomposa, but he left there around the year 1025 because the people there did not believe his beliefs and resisted his ideas. Guido was asked to be a teacher of a cathedral school by the bishop of Arezzo. Guido constructed the idea of having an actual four line staff, before Guido they used a red F-line and a yellow C-line and Guido added a line between the two lines and one above the C line. This made it so much easier for new musicians to learn music. He also used letters for clefs, the treble clef, G clef, and