Which composer is given credit for inventing chant notation on a staff?

Guido D’Arezzo

Explanation:

    The music theorist, Guido d'Arezzo (992 - 1050) was an Italian monk and conductor of the choir of the Cathedral of Arezzo, Tuscany, having bequeathed a more advanced musical notation to the West. It is due to him, in particular, the name of the notes - ut, ré, mi, fa, sol, lá, si - based on a hymn to Saint John in Latin, as well as the musical score - the pentagram - in force until the our days. In addition, he was the real initiator of solfeggio, an exercise to learn to read notes, usually marking the compass with his hand.