The subject of this book, as per the title, is music (from the Greek μουσική τέχνη - musiké téchne, i.e. "the art of the muses") in the works of Pythagoras, the first intellectual in the history of Philosophy to make that art the center of their worldview, even including it in the so called "Exact Sciences". In order to have more comprehension and clarity with regards to the intellectual production of Pythagoras, whose written works survived to the 21st century in a very fragmented form and in much smaller number, it is necessary to research the historical sources contemporary to the philosopher, as well as those which succeeded him.