In Close Encounters of the Third Kind, music bridged the gap between worlds, but music may not actually be the key to interspecies communication. Researchers have found that tamarin monkeys don't respond to human music, only music created for monkeys.
Charles Snowdon, a professor of psychology at the University of Wisconsin-Madison, and David Teie, a musician at the University of Maryland, have been testing the responses of cotton-top tamarins to different kinds of music. In the past, psychologists trying to examine the evolutionary roots of music have played music for primates, but with little response from our hairy cousins.
The problem, Snowdon and Teie claim, is that human music is designed for human enjoyment; different species interpret rising and falling pitches, and the duration and volume of sounds differently, so what's melodious to human ears may sound like random noise to a monkey or an ape. They tried instead to compose music based on tamarin calls, and, sure enough, when monkeys heard music based on the "fear" sounds, they became agitated and nervous, but when they heard music based on the "friendly, happy" sounds, they became visibly calm and relaxed. They hope their study will open a new door in animal communications research, one in which behaviorists not only communicate information to animals, but also use sounds to change their long-term behavior.
Like earlier psychologists, Snowden and Teie played human music for the tamarins, to no effect — with one exception. They reported that the monkeys did, in fact, respond to Metallica, though it's not clear whether they saw it as "fear" music or "friendly" music.
You can hear samples of David Teie's monkey music compositions at PhysOrg.