How can a piano tuner obtain such high precision with no other measuring device than their own ears? How can a sequence of notes seem to rise continuously despite coming back periodically to the same notes? What are the possibilities and the limits of digital sound? These are a few examples of questions that are discussed in this book, which presents an overview on the nature of musical sounds, from their production by acoustic music instruments to synthesized sounds obtained with computers. The topics that are treated include sound propagation, Fourier and time-frequency analysis, psychoacoustics, analog and digital signal processing theory, computer science and MP3 sound compression, and of course... music!