The melodies of folk songs can be predicted depending on culture

A research group in Keio University, including Associate Professor Patrick E. Savage, Research Associate Samuel Passmore, Associate Professor Haruo Suzuki, and Gakuto Chiba, masters student at the Faculty of Environment and Information Studies, investigated melodies of 10,062 folk songs and showed that melodies of folk songs can evolve through a certain system of changes, and found that they are subject to some predictable changes peculiar to each cultural environment, using alignment algorithms developed by molecular geneticists. For example, musical notes with stronger rhythmic functions are less likely to change than grace notes and are likely to be added or deleted rather than changed to other notes by performers. Substitution, if any, is likely to occur to an adjacent note. From these results, the research group revealed that creative artistic forms like music are subject to some regular evolutional constraints peculiar to different cultures, which is similar to those that govern the evolution of genes, language and other cultural domains. These research results were posted in Current Biology.

In order to understand the diversity of cultures in the current age, human history researchers have begun to pay attention to the Theory of Evolution more than ever before. However, it is unknown yet whether the process of cultural changes proceeds in the same way in different societies. Folk songs are both culturally universal and changeable, as they evolve musically and are repeatedly transmitted between individuals over a long period of time.

The research team picked up and analyzed 10,062 folk songs (including 4125 folk songs in the U.S. and UK and 5937 Japanese folk songs), including some famous music such as 'Scarborough Fair' and 'Soran Bushi.' Associate Professor Savage manually translated melodies of these folk songs into character strings to form sequence of notes similar to gene sequences. "It took time to transform melodies into character strings, but it was quite fun, because I encoded them while humming," he said. Thanks to the encoded music, alignment algorithms originally made by molecular geneticists was made applicable, which allowed the group to identify 328 sets of highly related melodies for a more detailed analysis.

Using the highly related melodies, the research team investigated how music changed from one recording to another and reflected the information into some evolutional patterns. It is believed that musical notes with stronger rhythmic functions are less likely to change than pure grace notes, while notes having stronger stress than the final note were also unlikely to change, according to the team.

On the other hand, unstressed notes and grace notes are most likely to change. Moreover, musical notes are likely to be added or deleted rather than changed. This reflects that a musical performer (a singer) will not change musical notes that form the entire melody, while he/she would add, delete and/or substitute grace notes freely. It also means a singer is likely to select an adjacent note for substitution, if any, in the musical scale.

This research result suggests that there is a certain cultural system that is subject to some constraints, as there are broad patterns of regularities in different cultures, though subject to some cultural variations eventually. The research team says that there are two major mechanisms, kinetic constraints and cognitive constraints. The kinetic constraint refers to the idea that a substitution of a musical note, if any, is likely to occur to an adjacent note, due to some physical limit of a performer. In other words, a musical note is more likely to move to a note nearby than to a note far away from it. Or even if a performer could make a greater change, it is less likely for him/her to notice small differences between performances due to cognitive constraints regarding pitch, note value, and perception.

These findings indicate that a creative artistic form is subject to constraints by certain evolutional mechanisms similar to that is seen in biology, genetics and other cultural domains. According to the research team, general principles may be applicable to changes of folk songs, but in reality, its concrete mechanism may greatly vary among them. It is therefore necessary to explore relative influences of cognitive and kinetic processes on evolution of melody and interaction of micro and macro level processes in performing music.

"We are very excited that our experiences from performing could be used to quantify the cause for melodies we felt influential for evolution, and we are also investigating how lyrics, physical appearance and other non-musical properties of performers are important in conveying and evolving music," said Associate Professor Savage and Mr. Chiba, who have previously received awards as performers of Japanese folk music.