The article is written on the basis of a conversation on the philosophy of music by Professor G.G. Kolomiets, author of the book Value of music: philosophical aspect, with a musician from France, Dmitry Rasul-Kareev, Clarinet solo of Orchestra de la Suisse Romande. The dialogue gives a detailed and simple understanding of the philosophical view of music on the example of the ancient philosopher Pythagoras. His cosmological teaching saw the kinship of music, mathematics and philosophy and stated that the divine perception of the world is contained in the divine Number permeating the entire cosmos and our life. Music is made of numerical proportions and acts as a substance that exists even without a person, yet this unchanging principle of divine harmony, can be felt, experienced and expressed in musical art. Cosmologists believed there is a comprehensive law, according to which objects obey the divine mind, the great Rhythm. Music seemed to be the embodiment of the rhythm of the universe and harmony. The essence of the harmony of the spheres is that the cosmos is a harmoniously arranged and musical-sounding body. The movement of the starry sky creates the music of the cosmic spheres, which is refracted when playing musical instruments, and this lends itself to precise mathematical calculations. The intervals between the cosmic spheres are mathematically correlated with each other like the intervals of tones in music. The Pythagorean understanding of the numerical harmony of the structure of the universe largely determined the path of development of music theory, forming the main musical categories: fret, rhythm, interval, modulation and others. The modern philosophy of music deepens the Pythagorean ideas of harmony of spheres, putting forward the principles of functionality and processivity as properties of music, and allows us to talk about the law of cyclicity on a global scale. For example, following Pythagoras, music outside of the actual musical art is interpreted as a reflection of the vibrations of a complex communicative system: man-society-nature-cosmos.