Tonality can be explained as a system of tonal relationships that shape melodic objects and maintain their unity. Tonal modulation is a re-orientation from one tonality to another within same musical composition. Modulation is the principal tool of thematic development in the European musical tradition. Musical practice shows that some modulations are more popular than others and that some modulations produce strong emotional effects. We suggest that affective responses to tonal modulation depend on degree of modulation, on direction of modulation along the circle of fifths, and on the involvement of the major and minor modes. We conduct two experiments to investigate affective responses to tonal modulation by asking the participants to indicate intensity of their affective response to each stimulus on six bipolar adjective scales related to valence, synaesthesia, potency, and tension. EXPERIMENT 1 examines affective responses to all twelve major and minor keys of the Western tonal schema. EXPERIMENT 2 focuses on modulations to three selected steps in the major mode only and compares affective responses to artificial stimuli (harmonic progressions) with responses to real music excerpts. In addition, EXPERIMENT 2 investigates affective influence of the direction of pitch-change in soprano and bass melodic lines in the harmonic progressions. Results demonstrate different affective responses to different degrees of modulation. Results also agree with other studies on affective response to the major and minor modes. Listeners recognize modulations to the important dominant and subdominant steps and sense the negativity of the tritone. It is found that responses agree with the theoretical model of pitch proximity and that they are influences by the direction around the circle of fifths. Results indicate that in harmonic progressions responses were influenced by melodic contour patterns and that in real music excerpts affective influence of degree of modulation can compete successfully with other expressive elements of music such as tempo, tessitura, and style.