This volume deals with emotional differentiation, with differentiation of affects, and with regulation of affects in music therapy. Therapists generally address their attention to the manner in which the emotional expression changes, is refined, or is broken in the course of therapy. Music therapists have special access to the emotions of patients through their continuous use of music. In previous centuries, it was already assumed that joy, sorrow, and pain could be expressed through music, and that music could also call out these emotions. Specific compositional stylistic elements have been used to produce specific emotional expressions. These types of experiments were observed already during the Renaissance, and during the Baroque period there were various theorists entrenched in affective teaching. The essays collected here attempt to build a bridge from the baroque affective teachings to contemporary music therapy and provide an overview of the state of today's research on emotion.