The team then played these songs to 750 volunteers recruited through the internet—a third from the United States, a third from India, and another third from a mix of 58 other countries. Every participant listened to 36 recordings, and rated how likely each one was to be, say, a dance song or healing song.

They were surprisingly accurate, for every category except love songs. Dance songs and lullabies, in particular, share enough features around the world that naïve listeners can identify them with no experience of the cultures from which they arise. The three groups of volunteers were also surprisingly consistent. “Some random person from Texas who’s doing our survey is expected to have a similar conception of what a healing song should be to someone at her computer in India,” says Singh.

In many ways, the Natural History of Song is a 21st-century take on a grandiose project from the 1960s called Cantometrics. Led by ethnomusicologist Alan Lomax, the Cantometrics team systematically analyzed 4,000 songs from 400 cultures around the world according to 37 factors—everything from group cohesion to breathiness to rasp. It was a massive attempt to statistically link the traits of the songs to the characteristics of the cultures that produced them.

The problem is that the Cantometrics collection “wasn’t built in any systematic way,” says Mehr. “It was just a collection of lots of interesting music from all over.” To create something more representative, he and his colleagues deliberately sought out song recordings from 30 regions that cover the whole globe. On a shoestring budget, they contacted anthropologists and ethnomusicologists for any unpublished recordings, and scoured libraries for published ones. “I know we annoyed the hell out of the librarians in [Harvard’s] Loeb Music Library,” Mehr says.

They also annoyed a lot of ethnomusicologists. When the team announced the Natural History of Song project on the Society for Ethnomusicology listserv in late 2016, some members accused them of “denying human agency and geopolitics in [the] very title” while others worried that the project sounded like a colonial “search for the pristine.” “It’s like because we’ve taken up a question that hasn’t been asked for a long time, we were portrayed as mid-century armchair anthropologists with many assumptions, some of them racist,” says Singh.

This backlash has its roots in the reaction to Cantometrics. Many ethnomusicologists felt that the team’s quantitative analysis was insensitive to the cultures that their 4,000 songs came from. The project created a backlash against the search for universal qualities, in favor of focusing on subjective, individual experiences.

“I am skeptical of this sort of attempt to impose order on humanity’s music making by scholars with relatively little on-the-ground ethnographic experience,” says David Locke, an ethnomusicologist at Tufts University. In the West African songs he studies, songs of very different styles can be repurposed for all kinds of functions. “Songs associated with war or death can be sung to soothe an infant—but there would not be a thunderous drum ensemble and full dance ensemble present,” he says. “When I teach courses that ask students to listen to unfamiliar music, they usually make wrong associations between the singing style of the selection and its use in human life.”