This thesis examines listeners' responses to tonal and atonal music through a combined model that encompasses music perception theories such as the cue abstraction mechanism, and both listener- and stimulus-based models of emotional responses to music. Aspects of this model relating to listener features and structural features are examined in more detail through an empirical investigation of the effects of musical experience and familiarity on perceptual and emotional responses to tonal and atonal music. Previous empirical investigation of these areas is limited: research concerning the effects of familiarity is largely unsystematic or explores the effects of immediate repetition of music on listeners' emotional responses; and research concerning emotional responses to music generally focuses on tonal repertoire. This empirical work encompasses a novel longitudinal mixed-methods approach to investigate listeners' changing emotional responses to music by Clementi, Schoenberg and Berio. Results suggested that musical experience increases listeners' perceptual efficiency, and influences emotional responses: music students' responses to the three pieces were at similar levels, whereas non- music students' responses varied more widely between the three pieces. With increasing familiarity, participants showed evidence of greater understanding of the structure of the music and greater awareness of details of the music. A significant ANOVA indicated changes in emotional responses wth familiarity, and the triggers of these responses changed according to the participants' awareness of musical features. The number of associative sources of emotional responses also increased. Anticipatory emotional responses developed with familiarity, particularly in response to the Clementi. There were interesting differences between participants' responses to the tonal and atonal pieces. Participants found it easier to identify the musical structure of the tonal piece than the atonal pieces, and all participants felt more familiar with the Clementi than the Schoenberg and the Berio. Participants' overall levels of emotional responses were highest in response to the Clementi, followed by the Schoenberg and then the Berio, and triggers for these responses varied in importance for each piece. These results indicate that musical expertise and familiarity should both be considered as important variables in future research, and that responses to atonal music merit further investigation in the future.