The monograph, along with an overview of ancient and later ideas about harmony, shows the role of the works of K. Marx, F. Engels and V.I. Lenin in creating the methodological foundations of a new, dialectical-materialistic, concept of harmony and harmonic development. On the basis of the laws and principles of materialistic dialectics, the connection of harmony with contradictions, the role of correspondence, symmetry and rhythm in harmonic development are considered. The specifics of harmony and harmonic development are revealed on the basis of an analysis of a large historical, philosophical and scientific material. The publication is designed for philosophers and specialists in the field of natural science and social science.