This small volume aims to summarize briefly the main facts of musical theory, to visualize them in a series of 80 tables of practical use. Such a summary can obviously only retain the basic structures, the basic mechanisms of music. The elements of counterpoint and harmony, as well as the nomenclature of the instruments, are reduced to their simplest expression. We will not find in this Aide-Mémoire the notions of acoustics, nor the historical explanations that are so necessary to the understanding of musical texts. Marcel Bitsch and Jean-Paul Holstein.