科学美国人60秒--生活和艺术之间的相似之处

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Researchers Analyzed² Folk Music like It Was DNA³: They Found Parallels between Life and Art

Using software designed to align⁴ DNA sequences, scientists cataloged the mutations that arose as folk songs evolved

Karen Hopkin: This is Scientific American’s 60-Second Science. I’m Karen Hopkin.

You’re probably familiar with the concept of evolution. Living things evolve by accumulating genetic⁵ changes, which are then weeded out or preserved through a process of natural selection.

Turns out the same thing happens in music. And by using the same software that’s used to track mutations in genes⁶, researchers have mapped out the sorts of changes that shape the evolution of songs. The findings appear in the journal Current Biology. [Patrick E. Savage⁷ et. al, Sequence alignment⁸ of folk song melodies reveals cross-cultural regularities⁹ of musical evolution]

Patrick Savage: I’ve always loved music since I was a child.

Hopkin: Patrick Savage, an ethnomusicologist at Keio University in Fujisawa, Japan.

Savage: I grew up singing English folk songs. My dad really likes folk music and often has his friends come over and do jam sessions at home. Then, when I moved to Japan about 11 years ago, I started studying Japanese folk songs. And I really liked that repertoire¹⁰, too.

Hopkin: The style was very different from the music he grew up with.

Savage: So, like [sings tonal sounds].

Hopkin: Yet the way the songs are learned, by trying to imitate a recording¹¹ or a teacher, is pretty much the same.

Savage: So it made sense to test these ideas about “Are these general evolutionary¹² rules that we find in music, especially in these folk songs, repertoires¹³ I know, that would kind of parallel what we find in genetics and allow us to get a more sort of general unifying¹⁴ theory about music and evolution across different cultures?”

Hopkin: At first, he and his colleagues hoped to tackle a huge reconstruction¹⁵ of the family tree of all folk music.

Savage: But kind of quickly, [we] realized that it was very—it would be quite challenging to do because when you build these phylogenies, these family trees, you kind of have to make a lot of assumptions about how the process works.

Hopkin: So, for example, geneticists know what kinds of mutations crop up in DNA—and with what frequency—information they can then use to assemble and calibrate¹⁶ their gene-based phylogenetic trees. But Savage says they didn’t have the same level of knowledge for music.

Savage: So we decided¹⁷ that, rather than try to do the big reconstructions¹⁸, we would first focus on the simplest case, which is the pairs.

Hopkin: Savage and his team combed through enormous catalogs of English and Japanese folk songs to identify pairs of melodies that were clearly related—like two different versions of the song “Scarborough Fair,” which is actually based on a traditional English ballad¹⁹ about an elfin knight²⁰.

[CLIP: Woman sings “Scarborough Fair”]

Savage: With the English ones, people had been going out there and notating things by ear since at least the early 1900s.

Hopkin: And by the mid-1900s, a similar process had begun in Japan.

Savage: They just kind of sent teams of scholars out throughout all of Japan and said, “We need to collect all the folk songs before they disappear.”

Hopkin: So Savage had a pool of some 10,000 tunes²¹ to work with.

Savage: I just had to go through and just and look at the notations²² in the anthologies and kind of sing them to myself as I converted them into these sequences of text—Cs and Ds and Gs and things like that—so we could run the sequence alignment algorithms on them.

Hopkin: So what did team Savage learn? Well, a few things.

Savage: One was that more functional²³ notes, notes that had stronger rhythm functions, would be more stable.

Hopkin: So notes that are key to the melody.

Savage: You listen to “Scarborough Fair,” the end, you know, “She once was a true love of mine.” The final note is a very strong downbeat. And it’s also the last note where you’re kind of always expecting a note. So very rarely would you end on like “She once was a true love of mine.” It feels very unfinished. Likewise, you would never expect that note to just be deleted. You wouldn’t expect “She once was a true love of....” That would just be very strange.

Hopkin: Next, they found that when one note mutates to another note, the changes tend to be small.

Savage: So like one or two semitones above or below where it would have been rather than six or seven semitones. Which would be a difference of like, [sings] “la la” versus²⁴ like [sings] “la la.”

Hopkin: Here, for example, Savage sings snippets of a Japanese lullaby.

Savage: These ones have different lyrics²⁵ but almost the same melody. The first one was notated from the singing of Tonsui Kikuchi. And it sounds something like this [sings].

And the second one, notated from the singing of Shigeri Kitsu, sounds like this [sings].

So the differences there, for example, the last one [sings] versus [sings] are very small, just a semitone difference, but [they are] an example of a small substitution distance.

Hopkin: Such small substitutions have minimal²⁶ effect on the overall melody. So they’re the essentially²⁷ the musical equivalent of what geneticists call a “neutral mutation,” one that doesn’t alter an organism’s fitness.

Now, all that seems pretty straightforward²⁸. But the next finding was a bit of a surprise.

Savage: There’s two different kinds of mutations you can have in genetics or music. The substitutions are one-note changes to another note. Or you can have an insertion or deletion where a note is either inserted or deleted from the sequence or a nucleotide is inserted or deleted from the sequence. In genetics, these are very rare.

Hopkin: That’s because the instructions carried by genes are read in sets of three nucleotides. Add or remove just one, and you throw off the whole register, which messes up the rest of the message.

Savage: But we found, in music, insertions/deletions were actually quite a bit more common than the substitutions.

Hopkin: That’s because they can easily be accommodated by holding other notes longer or singing some faster, leaving the melody intact. So in one version of “Scarborough Fair” ...

Savage: So Martin Carthy kinda sings, “Parsley sa-a-age, rosemary and thyme.” And Simon and Garfunkel just sing “parsley, sage²⁹, rosemary and thyme.” So, this little “sa-a-age” ornament³⁰ is just deleted. But they just sing the “sage” a little bit longer, and it takes up the same amount of rhythmic³¹ space.

Hopkin: Savage says that many of these mutations, like their genetic counterparts, are probably accidental.

Savage: That’s what I do when I learn songs. I’ll be learning from my singer, and then I’ll record myself singing, and I’ll realize that I’ve sung a couple of notes a little bit different—a little bit higher here, a little bit lower there. Or I added an extra note by accident. I’m usually not consciously trying to change what my teacher has sung. But it’s just easy to crop up.

Hopkin: Using a genetic approach to analyze¹ melodies also has some practical applications.

Savage: We can apply these sequence alignment techniques to quantify how similar two songs are and how likely the changes are to happen and sort of have little bit more quantitative³² evidence for these high-profile multimillion-dollar [copyright] cases like “Blurred Lines” or George Harrison’s case with the Chiffons and “My Sweet Lord”/“He’s So Fine.”

Hopkin: At the same time, Savage looks forward to continuing to explore music’s ancestral roots as a scientist and as a musician.

Savage: Everyone’s always inspired by the great musicians of the past. But, like, these currents of evolution go back hundreds of thousands of years. So, yeah, it’s kind of this sort of connection with other humans through music at a very deep level and throughout time is one that kind of excites me as a performer.

Hopkin: And it makes his science sing.

[CLIP: Patrick Savage and Gakuto Chiba sing the same Japanese folk song, “Kuroda Bushi”]

Hopkin: Special thanks to Pat Savage and his student Gakuto Chiba for their vocals³³. And a final note on “Scarborough Fair.” The first version you heard came by way of Wikimedia Commons user Makemi. We’ll include a link to that recording in the podcast transcript³⁴. And our bonus, hidden track was sung by Mrs. G. A. Griffith in 1939, recorded by John and Ruby³⁵ Lomax.

Hopkin: For Scientific American’s 60-Second Science, I’m Karen Hopkin