A poster presented at MidBrains 2009, a regional undergraduate neuroscience conference at Macalester College, St. Paul, MN, May 2, 2009 Recent evidence indicates that changes in heart rate accompany brain activation in emotion (Arce et al. , 2007; Lane et al. , 2008). The present study investigated these changes using 1 2 musical excerpts. In one set of 7 songs presented to all 35 participants, a song designated as the original was used in a music search engine (Manaris et al. , 2008) to find 3 similar and 3 dissimilar songs based on the melody and timbre of the original. Five other songs were selected in a similar fashion using an original song from one of the participantâ€™s three favorite genres. During listening, EEG and peripheral psychophysiological activity were continuously measured. After each song, subjects rated their liking of the music and their own activation and pleasantness. Pleasantness and liking ratings were significantly higher for similar than for dissimilar pieces, while activation tended to be lower. Heart rate responses to these pieces also differed - significantly longer inter-beat intervals and higher heart rate variability for the dissimilar than for the similar songs. These findings indicate that heart rate changes, together with frontal cortical activation (Siebert, 2009), are components of the differing affective responses and that search engine choices reliably predict affective responses to music.