Bryce Richter / UW-Madison

Cotton-top tamarin monkeys grew calmer after they heard music based on their own calm, friendly calls. But the monkeys became more agitated when researchers played music that contained elements of their own threatening or fearful calls. Listen to arousing monkey music and calming music (Copyright David Teie).

Music may have charms to "soothe the savage breast," but that doesn't mean the same music that soothes humans will charm other species. Monkeys, for example, aren't much affected by human music.

To find out whether any kind of music could affect a monkey's mood, a musician and a primatologist created tunes tailor-made for cotton-top tamarins. They report that the experiment worked - but the melodies are unlike anything you've ever heard.

The music that mellows out a monkey consists of long, high-pitched tones that sound squeaky to human ears. "To me, that sounds like fingers scratching on a blackboard," said Charles Snowdon, a primate researcher from the University of Wisconsin at Madison.

At the other extreme, the monkeys' equivalent of a thriller-movie soundtrack sounds like a fast-stuttering engine, overlaid with string-quartet screeches. "I can't even imagine dancing to it," Snowdon said.

But based on the reviews reported in this week's issue of the journal Biology Letters, the tamarin tunes were a certifiable hit.

Researchers played an assortment of music for seven pairs of adult tamarin monkeys housed at the University of Wisconsin. Most of the run-of-the-mill human music, ranging from Samuel Barber's "Adagio for Strings" to Metallica's "Of Wolf and Man," had little effect (although strangely enough, the monkeys were calmed somewhat by the heavy-metal music).

In contrast, the music custom-made for the cotton-top tamarins produced significant effects within five minutes: After hearing the mellowing-out music, the monkeys moved around less, interacted less and foraged more. After hearing the thrilling, threatening tune, they moved around more, huddled together and seemed more anxious.

All this was music to the ears of David Teie, the University of Maryland musician (and National Symphony Orchestra cellist) who composed the monkey music. "I was pleased, in a strange kind of aesthetic way," he told me.

For years, Teie has been working on a theory looking at the relationship between music and emotional vocalizations. In his view, music distills the meanings of sounds we make when we soothe a baby ("awwww," starting with a high pitch that slides slowly downward) or warn our mates about danger ahead ("Look out!" in sharp, staccato tones and a rising pitch).

"If I was right about the aspects of music that was built for humans by humans, then I should be able to write for another species, based on its perceptions and development," he said.

So Teie got in touch with Snowdon and began the process of analyzing recorded monkey vocalizations. He enlisted other musicians to categorize the sounds in terms of pitch, tempo and tonal progression, while Snowdon helped interpret which behaviors were associated with which sounds.

Teie said "there was a general consensus" about the linkages between different sound patterns and their effects: Long tones, in a rising or falling pattern, were associated with soothing behaviors. Quick, noisy staccato notes with broad sweeps in pitch should have an agitating effect.

One big twist is that the monkeys' "sweet spot" is much higher in pitch and much faster in rhythm. "Their communication is so fast and so high that it all sounds like chirps to us," Teie said. To make sense out of the monkeys' recorded calls, he slowed the tempo down to an eighth of normal, and brought the pitch down three octaves.

The result is that even the calming music that Teie composed sounds high-pitched and up-tempo to humans. And that's part of the point: Music can soothe the savage beast, but it works best if it's written for the beast rather than for the humans.

"If I'm irritated by that finger-scratching monkey song that calms them, then playing soft rock or country may not have the appropriate effects on the monkeys," Snowdon said. "So what do the animals like or dislike?"

To follow up on the research, Teie has created a Web site known as "Music for Cats," which offers tunes written for tabbies. He's also been talking with zoo curators about the possibility of providing captive animals with species-specific background music.

"We now know that it's possible to bring the enjoyment of music to other mammals," he said over the telephone from the Czech Republic, where he's touring. "I just visited the Prague Zoo yesterday, and let's face it, they're just desperately in need of enrichment. It would be possible to bring enrichment with no cost and absolutely no risk."

For now, he's hoping that folks will play the tunes on Music for Cats for their kitties and let him know which music gets the best feline response.

"I am very interested to get an overview of the responses, and I would want to keep writing the music that gets the best response," he told me. "I want genuine and honest feedback. If someone finds that their cats jump, scream and run out of the room, I'd want to know that."

Feel free to pass along your reviews of Teie's music for cats, or his music for monkeys, in your comments below.

Update for 9 p.m. ET: One natural question to ask is, why make the effort? If you listen to the sounds that an animal makes, and then create a type of music based on those sounds, isn't it natural that the animal would respond to the music as it responded to the original sounds? I got several answers on that point. First, from the paper itself:

"A simple playback of spontaneous vocalizations from tamarins may have produced similar behavioral effects, but responses to spontaneous call playbacks may result from affective conditioning. By composing music containing some structural features of tamarin calls but not directly imitating the calls, the structural principles (rather than conditioned responses) are likely to be the bases of behavioral responses. The results suggest that animal signals may have direct effects on listeners by inducing the same affective state as the caller. Calls may not simply provide information about the caller, but may effectively manage or manipulate the behavior of listeners."

Snowdon explained it another way in today's press release, saying that even among cotton-top tamarins, communication is about much more than just information:

"I am not calling just to let you know how I am feeling, but my call can also stimulate a similar state in you. That would be valuable if a group was threatened; in that situation, you don't want everybody being calm, you want them alert. We do the same thing when we try to calm a baby. I am not just communicating about how I am feeling. I am using the way I communicate to induce a similar state in the baby."

The findings about "monkey music" may shed light on the roots of human music as well, Snowdon said:

"The emotional components of music and animal calls might be very similar, and from an evolutionary perspective, we are finding that the note patterns, dissonance and timing are important for communicating affective states in both animals and people."

Teie, meanwhile, framed his answer in artistic terms:

"One question I am often asked is, 'Isn't this just you mimicking these calls on the cello?' Part of the idea is that it's not exactly the thing. ... As long as you don't know what it is, it will tend not to be subject to habituation, and it will always get to you."

Update for 9:15 p.m. PT: OK, one more thing. I asked Teie if there were examples of vocalizations or musical styles that had different meanings for humans and for monkeys. He pointed to the example of the "Ohhhhh" sound that expresses sympathy or consolation - you know, the kind that starts out at a high pitch and slowly slides to a quieter, lower pitch.

"We don't have the opposite," he said. "We don't have an emotionally generated vocalization that slides from lower to higher. Well, it means something specific to tamarins. It has a kind of enlivening factor to it. When they go up a major third, fourth or fifth, these are the affectionate calls from mother to young."

All I can say to that is, Ohhhhhh?

Update for 3:35 p.m. ET Sept. 5: In an e-mail, Teie adds a little bit to the human-vs.-tamarin vocalization discussion:

"At the risk of being petty - the upward-sliding 'oh?' is an extract from non-tonal Indo-European language and not an amygdala-generated vocalization. And the specific contour of upwardly sliding vocalization that tamarins have and we don't is one that gets louder as it gets higher: 'ooOOH!' Try that one in conversation and I think you'll get some funny looks!"