Wishing to give pleasure to all those who love music, I have considered and thoroughly investigated everything related to all sounds that make harmony and are able to create concord and consonance to be judged by the sensibility of the ear. I have been able to find nothing save what has already been created, and having thought it over carefully, [I believe that] it is impossible to create anything new which is not derived from the four universal sounds. They are: first, the human voice; second, the sound of the organ, which comes from air and wind; third, the sound of strings, whether of steel, gold, silver, brass, or gut; and fourth, the sound of the hammer, which is the sound of bells and of the drum. Beyond these four it is impossible to discover any others.

It might be objected that birds possess quite pleasing and delightful voices, and even that some speak and sing songs quite well, which is true. But these songs must not be elevated to the category of music, given that birds do not and cannot create either harmony or consonance. To create harmony, there must be two or three voices that produce various intervals and sound in proper tune according to the judgment of the ear. To attempt to attribute this to birds would be crediting them with the use of reason.