The article is concerned with the question whether music is accessible to rational investigation. The musicological answer is reduced to the efforts to examine what happens in the musical act because it is the only event in which the relation with music is possible. The musical act is the defining moment, but the tradition of rational investigation has always been associated with the possibility of a self-contained investigation of this act as a set of elements, characteristics and regularities. This tradition is born in the philosophy of Antiquity as an attempt to deduce terms and conditions for music, which do not match the spontaneity of the musical act and the immediate rendez-vous with music. Among all types of rationality, only the musicological rational has the advantage of being capable of seeing musical „rigor" (accuracy, order, etc.) as supra-rational, insofar as it goes beyond the theoretical rigor and testifies to regularities of a completely different order. The question of the rational in music is valid only because the musical act follows regularities, but musical regularity (Gesetzmäßigkeit) is beyond the regularities accessible to the rational.