<title> SUMMARY </title>The leit-motiv of the present description of the relationship between music and natural philosophy in Italy in the seventeenth century is a recurrent theme: the mathematical or « Pythagorean » approach to music as opposed to the experimental or « Aristoxenian » approach. During the sixteenth and seventeenth centuries this opposition, rendered pertinent by the cultural transformations that accompanied the consolidation of modern science, gained in complexity and took on original forms and meanings. The present paper, in the first instance, outlines the major traditions of classical musical thought and its medieval heritage. Secondly, it provides a survey of the more significant attempts at renewing musical theory that were carried out during the second half of the Cinquecento in the light of the Italian renaissance of mathematics of the XV and XVI centuries. It continues with an examination of the musical ideas of Galileo and offers a primary documentation of the interest displayed by representatives of the Galilean school in the science of sound during the first half of the Seicento.Finally it discusses, for the first time, the theories of sound of F. M. Grimaldi and D. Bartoli and the musical doctrines of P. Mengoli within the framework of the principal philosophical elements of Italian culture between 1660 and 1680.