This book addresses fundamental issues of music development for both children and adults. It is a concise handbook that analyzes in a critical, sociological and evaluative way the multidimensional nature of musical behavior. It follows two basic guidelines: it provides an overview of research data, different theories and methodologies related to the development of music, while providing a theoretical framework for predicting the possible course of this virgin research field. The first chapters describe the main psychological approaches in the study of music behavior and analyze the musical development of preschool and middle school children in activities such as singing, listening, rhythm and melody, as well as the acquisition of a sense of harmony and of tonality. The last chapters follow a sociological approach and examine critical issues such as the development of the musical sense, creativity, musical currents and the influence of advertising. It is the first book that connects developmental psychology with music education, adopting a theoretical and practical analysis. It is addressed not only to the students of the departments of music, psychology and pedagogy but also to the music teacher who wants to be informed about the processes that determine the musical perception, thinking and musical performance of children.