German psychologist, idealist philosopher, music theorist. He was the founder (together with F. Brentano) of the European direction of functional psychology, one of the forerunners of phenomenology and gestalt psychology. The main direction of Karl Stumpf’s scientific activity is the psychological problems of the perception of sound tones and the related issues of music theory. One of the main concepts of Stumpf’s psychology of sound is the “fusion” of sounds: a multiplicity of sounds that form a single, integral consonance in the minds of listeners. Stumpf made the largest contribution to the study of psychological acoustics after Helmholtz.