As the deep, rich drone of a didgeridoo continued to emanate from a portable CD player, American composer Andrew Kaiser wrapped up his argument for the role of music in interstellar communication.

Speaking at a recent workshop in Paris, Kaiser echoed the sentiments of others at the meeting, stressing the fruitful interplay of art and science in constructing interstellar messages.

The workshop was one of an ongoing series of international meetings that brings together artists and scientists to discuss ways to create messages that might some day be transmitted across interstellar space, whether by radio signals or laser pulses. The meetings provide advance preparation for one of the most critical decisions that would face humankind if the Search for Extraterrestrial Intelligence (SETI) should some day succeed: should we reply, and if so, what should we say?

In Kaiser's view, the structure of terrestrial music might provide clues to creating interstellar messages that could be understood by extraterrestrial intelligence. In the process, he suggests that music may provide a means of communicating "something of our consciousness that is essentially human, regardless of the civilization from which it emerges."

Kaiser is building upon an ongoing discussion about whether music would be understood by extraterrestrials. For example, astronomer Sebastian von Hoerner argued that extraterrestrials could even have music similar to Earth's - ;so similar that we shouldn't be surprised to find them using the same musical scales that we do!

Indeed, ever since the Pythagoreans of ancient Greece, we have known that there is an innate connection between music and math. Musical notes can be described in terms of precise frequencies, and harmonic combinations of these notes occur when their respective frequencies are in a precise ratio to one another. To the mathematician, the result is a simple fraction. To the listener, it is a harmonic sound.

While we cannot be sure that extraterrestrial beings will necessarily have a sense of hearing, any of the civilizations we contact in the course of a SETI detection will be savvy about some of the building blocks of music nevertheless. Concepts of frequency, amplitude, and duration are as basic to the construction of radio telescopes as they are to the composition of a symphony. Even if ET is deaf, the language of music might provide a means of access to terrestrial aesthetic sensibilities, through the intermediary of shared science.

Kaiser stresses the importance of avoiding ethnocentric biases when creating interstellar messages inspired by music. He notes that those from a Western tradition can easily assume that the conventions of classical music are equally applicable in non-Western cultures. And in many cases, they are not. Though concepts of harmony and melody are seen throughout the world, the forms they take may be radically different. In designing interstellar messages based on music, he contends, we should be careful in deciding which musical concepts to emphasize.

According to Kaiser, music also has the potential to express something that could give extraterrestrials insights into the human experience of being embodied: "The very physicality of the shared human condition lends itself to cyclic sonic concepts such as drone, repetition, silence: we breath, our hearts beat, lungs pump and eventually stop." If some day exchange messages with extraterrestrials who are not flesh-and-blood, but silicon-based artificial intelligence, it may just be that our music will provide them with some of their most important insights into what it means to be human.

By Douglas Vakoch