In this special issue of IEEE Signal Processing Magazine (SPM), we survey recent advances in music processing with a focus on audio signals. Eleven articles cover topics including music analysis, retrieval, source separation, singing-voice processing, musical sound synthesis, and user interfaces, to name a few. The tutorial-style articles provide an overview of theory and applications and discuss main advances. Although music processing has benefited a lot from traditional fields, such as signal processing, we hope to convince the reader that the rich and challenging problem domain of music also has many things to offer to signal processing and other research disciplines.