 Guido is credited with the invention of the Guidonian hand, a widely used mnemonic system where note names are mapped to parts of the human hand.However, only a rudimentary form of the Guidonian hand is actually described by Guido, and the fully elaborated system of natural, hard, and soft hexachords cannot be securely attributed to him.In the 12th century, a development in teaching and learning music in a more efficient manner had arisen.