The harp was the principal instrument in the churches till the organ appeared in the tenth century, a rough and barbarous instrument that had to be played with blows, and was supplied with wind from inflated skins.

Guido di Arezzo made a musical rule on the basis of Gregory's collection, and this was sufficient for the invention of the pentagramma[1] to be assigned to the Benedictine.
They continued to use the letters of Boccio and Saint Gregory as notes, but they placed them on lines of three different colours.

The imbroglio continued; to learn music badly took twelve years, and then they could not manage that singers from different towns could read from the same score.

Saint Bernard, dry and austere as his times, ridiculed this music as not being solemn enough; he was a man antagonistic to all art; he would have liked to see the churches dismantled and without any architectural adornments; and the slower the music was, the better it seemed to him.

He was the father of plain song, and he maintained that the more drawn out the music was, the more religious it became.