2003 0-7734-6928-1 This is an English translation of the authors’ Le Regole Della Musica: Indagine Sui Meccanismi Della Communicazione, published in Italy in 1999. It is divided into three parts. Part one discusses the concepts of ‘rule’ and ‘grammar’ in the general theory of musical communication, and the role of the computer in studying musical communication. In part two, the authors use a computer program they designed to make a concrete application of the theory. The computer analyzed the arias from a volume of cantatas by Giovanni Legrenzi, a 17th century composer. Based on the analysis, the computer was able to output artificial arias in Legrenzi’s style. (The aim of the program is not to compose new music, but to verify the correctness and completeness of the rules.) In part three, one aspect of the grammar is taken into consideration: the rules of melody. Starting from the grammar of Legrenzi’s arias, a general theory of melody has been developed and its validity has been tested on repertories ranging from Gregorian chant to Arnold Schoenberg.