Equal temperament vs. pythagorean tuning: a mathematical plot line

This paper presents a formal mathematical analysis of the structural logic underlying musical scales, focusing on the theoretical tension between Pythagorean tuning and Equal Temperament. Moving beyond a purely historical survey, the study adopts a mathematico-deductive framework to demonstrate how musical pitch systems emerge from fundamental arithmetic principles and the recursive generation of intervals.The analysis first axiomatizes the Equal Tempered system as a geometric partition of the frequency spectrum, exploring its algebraic properties and transpositional invariance. Subsequently, the Pythagorean system is formalized through the powers of the 3:2 ratio, highlighting the inherent conflict between rational purity and the necessity of a closed harmonic circle.A central contribution of this research is the systematic exploration of the number 12 as a ``fixed point'' in music theory. Utilizing the theory of continued fractions and Diophantine approximations, we provide a formal proof of why N=12 represents a unique multidimensional optimum. We discuss the ``bracketing'' property, where equal-tempered degrees act as a bridge between opposing Pythagorean ``shadows'' - a phenomenon that remains cognitively manageable at N=12 but leads to ``harmonic blurring'' in higher-resolution systems like N=53. Ultimately, the study frames the 12-tone system not merely as a historical convenience, but as a structural necessity for the evolution of Western polyphony.