The term ‘feeling tone’ occupies a foundational position in the depth-psychological corpus, appearing first and most systematically in Jung’s early experimental researches on word association, where it designates the affective charge — the quantum of libidinal energy — that binds a stimulus to a complex. In these laboratory investigations, feeling tone is operationally identified through prolonged reaction times: when a stimulus-word touches a complex, the feeling tone of that complex prolongs and distorts the association, often unconsciously. Jung’s later theoretical writings distinguish feeling tone from the discrete psychological function of feeling per se: the function is rational, evaluative, and discriminating, whereas feeling tone is an ambient affective coloring that may persist below the threshold of consciousness and spill across successive associations. In the typological literature, von Franz and Hillman extend the concept by exploring how feeling tones organize time experience — giving biography its qualitative texture, shaping moments into clusters rather than clock-sequences. Jung also employs the term aesthetically, as in his Picasso essay, where the presence or absence of a unified feeling tone in artwork distinguishes neurotic from schizophrenic production. Across these registers — experimental, typological, clinical, and aesthetic — feeling tone names the qualitative-affective signature by which psychic contents declare their complex-affiliation, their energic weight, and their gravitational pull on consciousness.