Abstract: When we listen to a melody, we rarely think of numbers, proportions or logarithms. However, we have often heard it said that music is mathematics. What is the relationship between the two disciplines? The connections are multiple, and manifest themselves in aspects such as symmetry, proportions, numerical relationships between frequencies and intervals, rhythm or the rules of harmony. In this talk we will present some of these topics, in a brief journey that will take us from Pythagoras to Xenakis.