Music is a contested aesthetic evaluation of what constitutes music. Music is an art, entertainment, or other human activity which involves organized sound. Definitions vary as music, like art, is subjectively perceived phenomenon. Its definition has been tackled by philosophers, lexicographers, composers, teachers, semioticians or semiologists, linguists, scientists, and musicians. Music is organized in time and consists of pitch, rhythm, harmony.


Musica instrumentalis, finally, was the lowliest of the three disciplines and referred to the manifestation of those same mathematical proportions in sound - be it sung or played on instruments. The polyphonic organization of different melodies to sound at the same time was still a relatively new invention then, and it is understandable that the mathematical or physical relationships in frequency that give rise to the musical intervals as we hear them, should be foremost among the preoccupations of Medieval musicians.

Musica humana designated the proportions of the human body. These were thought to reflect the proportions of the Heavens and as such, to be an expression of god's greatness. To Medieval thinking, all things were connected with each other - a mode of thought that finds its traces today in the occult sciences or esoteric thought - ranging from astrology to believing certain minerals have certain beneficiary effects.

Musica universalis or musica mundana referred to the order of the universe, as god had created it in "measure, number and weight".

The proportions of the spheres of the planets and stars (which at the time were still thought to revolve around the earth) were perceived as a form of music, without necessarily implying that any sound would be heard - music refers strictly to the mathematical proportions. From this concept later resulted the romantic idea of a music of the spheres.