The aim of the paper is to determine why copernicus made a personal seal of the ancient intaglio with the image of apollo playing a lyre, A representation illustrating the myth of phoebus the sun-God and his music as the source of the harmony of the universe. The reasons seem to be: a remarkable role played by the ancient opinions concerned with the harmony of the world in the creative process of copernicus' cosmological theory (his acceptance of "plato's axiom"), The (...) fact that in his theory the sun became the centre of the universe, And that a harmony of sounds, Supposed to be produced by the spheres moving under the rule of phoebus' music, Became--In his opinion--The real although not acoustical harmony of the simple circular spheres on which planets move in a uniform way around the sun. (shrink)