The role of symmetry in the good continuation ratings of two-part tonal melodies

Subjects heard a series of two-part melodies, in which each part was a random sequence of eight pitches (Experiment 1) or five pitches(Experiment 2) from the diatonic scale. The task was to rate each melody on how well the second part followed the first. It was predicted that the presence of symmetry between the two parts would increase the perception of good continuation. In Experiment 1, two symmetrical relat/lons—(itinversion) and (itretrograde)—yielded melodies that were more highly rated than the control melodies, which consisted of nominally (itdifferent) parts. A third symmetry, the (itretrograde inversion), did not enhance good continuation ratings. In Experiment 2, inversions and retrograde inversions were compared with control melodies, using shorter sequences and pitches with equal durations. Again, inversions, but not retrograde inversions, were significantly preferred. The results suggest that the aesthetic judgment of good continuation depends at least partially on a cognitive analysis of the relation between the melody parts. The positive symmetry effects are further discussed in relation to other studies of symmetry transformations in the contexts of both musical sequences and visual arrays.