We investigate non-verbal communication through expressive body movement and musical sound, to reveal higher cognitive processes involved in the integration of emotion from multiple sensory modalities. Participants heard, saw, or both heard and saw recordings of a Stravinsky solo clarinet piece, performed with three distinct expressive styles: restrained, standard, and exaggerated intention. Participants used a 5-point Likert scale to rate each performance on 19 different emotional qualities. The data analysis revealed that variations in expressive intention had their greatest impact when the performances could be seen; the ratings from participants who could only hear the performances were the same across the three expressive styles. Evidence was also found for an interaction effect leading to an emergent property, intensity of positive emotion, when participants both heard and saw the musical performances. An exploratory factor analysis revealed orthogonal dimensions for positive and negative emotions, which may account for the subjective experience that many listeners report of having multi-valent or complex reactions to music, such as "bittersweet."