This book (200 pages), by Fakher Hakima, lecturer and director of the Higher Institute of Music in Sousse, is an attempt to reveal a very particular thought that accompanies the musical act at the moment of its action, an act that takes place. relies on the hegemony of "meaning" and metaphysical talent as a motor. This book reflects the conviction that the musical act is not a random act, on the contrary, it is a logic oriented by the thought, the choices and the orientations of the composer, in relation to a grammar and an acquired musical style. This book is composed of two main chapters: a first chapter devoted to the analysis of "Active musical thought" as an instantaneous procedure at the moment of musical action and a second chapter comprising a socio-cultural study and an analytical and experimental musical study which discusses the modal/tonal dichotomy.