The intentionally ambiguous expression “Popular Music Browser” reflects the two main goals of this project, which started in 1998, at Sony Computer Science Laboratories. First, we are interested in human-centered issues related to browsing “Popular Music.” Popular here means that the music accessed is distributed widely and known to many listeners. Second, we consider “popular browsing” of music, i.e., making music accessible to nonspecialists (music lovers) and allowing sharing of musical tastes and information within communities, departing from the usual, single-user view of digital libraries. This research project covers all areas of the music-to-listener chain, from music description, descriptor extraction from the music signal, or data mining techniques, similarity-based access, and novel music retrieval methods such as automatic sequence generation, and to user interface issues. This article describes the scientific and technical issues at stake and the results obtained, and is illustrated by prototypes developed within the European IST project Cuidado.