To create music with more monkey appeal, Teie composed pieces using specific features in the tamarin calls, manipulating rising or falling pitches and the duration of various sounds. The music was inspired by sounds the tamarins make to convey one of two messages: fear and friendly affiliation.
When the music was played to seven pairs of adult cotton-top tamarins housed at the University of Wisconsin, the monkeys became more anxious and jittery when they heard the fearful monkey music. They then calmed down, and sometimes even foraged, upon hearing the affiliation-based music.
Regular human music was also played to the monkeys, which predictably showed little response, except for a very surprising, calming response to the heavy metal band Metallica.
Although birds, dolphins, whales and other animals produce what we call "songs," this study is among the first to show that a non-human animal can truly appreciate music.
"We think that the emotional communication part of music has an early history that predates humans," co-author Charles Snowdon, a University of Wisconsin professor of psychology and zoology, told Discovery News. "If music based on tamarin calls can alter their behavior, then our ancestors would have been able to use similar components of music to influence one another, and perhaps simple words to name things or to express actions."