This book draws a new perspective on music as a special form of cognition that provides growing children with the means to mediate their emotional state and attitude to suit their physical and social environment. My conclusions are based on new evidence coming from: 1) musicological analysis of the original and spontaneous vocalizations by children, selected to represent the milestones in the development of music cognition; 2) comprehensive research on "ear development" throughout early childhood, systematically conducted in the USSR/Russia on a large pool of subjects during the 1920-1980s; 3) data on music perception by people habituated to non-Western forms of music, including timbre-oriented music traditions of northeast Eurasia; and 4) research coming from Vygotskian school on sociogenesis and objectivization of musical sound in early childhood (published in Russian only). The principal objective of this book is to arm researchers and students with tools to analyze, interpret, and evaluate the patterns of tonal organization in children musicking - and to inter-relate these patterns to cross-cultural patterns of early verbal, social, and emotional development. Children’s musical cognition needs a thorough revision because of the old erroneous belief, still widespread amongst developmental psychologists, that the principles of Western tonality constitute a universal modus operandi, intuitively sought by children from birth. According to this view, early children’s musicking constitutes a “defective” implementation of adult’s music due to children’s deficiencies in vocal control and its coordination with hearing. In reality, early childhood musicking constitutes a peculiar type of music, different from adult’s music – very much like children’s early speech that follows its own principles, different from adult’s speech. The principles of children’s musicking ought to be inferred from the structural organization of their non-imitative attempts to make music - bottom-to-top (as opposed to the current "a priori" top-to-bottom method of describing children's music in terms of Western tonality). Some other important issues covered in this book are the goals of musical development in childhood, the issues of musical attrition, bimusicality, and normalcy of musical abilities, the modularity of musical hearing, and the relation between musical and real-life emotions.