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An iconic approach to communicating musical concepts in
interstellar messages
Douglas A. Vakoch
a,b,
a
Department of Clinical Psychology, California Institute of Integral Studies, 1453 Mission Street, San Francisco, CA 94103, USA
b
Center for SETI Research, SETI Institute, 515 North Whisman Road, Mountain View, CA 94043, USA
article info
Article history:
Received 21 February 2009
Accepted 6 January 2010
Available online 27 January 2010
Keywords:
Search for Extraterrestrial Intelligence
SETI
Interstellar communication
Interstellar messages
Interstellar music
Universal music
Polyphonic music
Iconicity
Cognitive modeling of music
abstract
Some characteristics of terrestrial music may be meaningful to extraterrestrial
civilizations by virtue of the connection between acoustics and mathematics—both of
which might be known by technologically advanced extraterrestrial intelligence. For
example, a fundamental characteristic of terrestrial polyphonic music is found the
number of tones used various scales, insofar as the number of tones represents a
compromise between competing musical demands; the number of tones in a scale,
however, also reflects some of the perceptual characteristics of the species developing
that music. Thus, in the process of communicating something about the structure of
terrestrial music through interstellar messages, additional information about human
perceptual and cognitive processes can also be conveyed. This paper also discusses
methods for sending signals that bear information through the form of the very
frequencies in which the signals are transmitted. If the challenges of creating intelligible
messages are greater than often thought, the advantage of reduced conventionality of
encoding the message by using an iconic format of this sort may be of significant value.
Such an approach would allow the incremental introduction of musical concepts,
somewhat akin to the step-by-step tutorials in mathematics and logic that form the
basis of Freudenthal’s Lincos.
&2010 Elsevier Ltd. All rights reserved.
1. Introduction
Some proposals for interstellar messages have begun
with systematic expositions of presumably universal
mathematical and scientific concepts in an incremental
manner from simple to complex. Indeed, the flexibility of
this approach is suggested by Freudenthal’s Lincos, which
progresses from basic arithmetic to discuss such varied
notions as time, space, and human behavior [2]. In the
current paper, an analogous approach based on a step-by-
step exposition of basic principles is suggested as a means
of constructing messages that bear structural similarities
to terrestrial music, in the process reflecting something
about the perceptual and cognitive nature of the compo-
sers of that music.
Perhaps the most widely known example of the use of
music for interstellar communication is the Voyager
recording, which contains encoded images, sounds, and
music of Earth. Although the primary intended audience
of this recording was terrestrial, this effort at expanding
people’s ideas of how we might communicate over
interstellar distances also attempted to provide clues that
might enable any extraterrestrial intelligence that inter-
cepts the recording in the distant future to begin to
understand its content.
For example, the recording’s introduction to the actual
musical selections was made via pictorial images of the
sort of instruments used to play the music, as well as
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/actaastro
Acta Astronautica
0094-5765/$ - see front matter &2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.actaastro.2010.01.006
Corresponding author. Department of Clinical Psychology, California
Institute of Integral Studies, 1453 Mission Street, San Francisco, CA
94103, USA.
Tel.: + 1 415 575 6244; fax: +1 415 575 1266.
E-mail addresses: dvakoch@ciis.edu, dvakoch@seti.org.
Acta Astronautica 67 (2010) 1406–1409
Author's personal copy
a graphic representation of the musical score. The hope
was that this would provide clues to help the recipients
comprehend how the music was physically produced.
The suggestion of using music to communicate with
intelligence beyond Earth has a much longer history than
the Voyager recordings. The 17th-century European genre
of the imaginary voyage provided a context for exploring
a variety of contemporary proposals for universal lan-
guage schemes. For example, the English prelate Francis
Godwin described a voyage to the Moon, in which the
terrestrial adventurer encountered strange lunarians who
communicated through a musical language. The inspira-
tion for this tonal language, however, was thoroughly
terrestrial—based on the Chinese language as described
by Jesuit missionaries recently returned to Europe. In the
case of Godwin’s lunar ‘‘language,’’ the musical system
was actually simply a method for translating letters of the
alphabet into particular musical notes. However, it did
preview more truly universal language proposals of the
next two centuries [3].
But would music really be intelligible to intelligent
beings evolved independently of humans on other
planets? Are the mathematical and acoustical foundations
of terrestrial music sufficient to provide a basis for
interstellar communication?
2. Universal scales?
The astronomer Sebastian von Hoerner provided one
argument in favor of the possible universality of at least
some aspects of music. He posited that if extraterrestrial
intelligence had indeed developed music, the form of this
music might share certain features with terrestrial music
[12]. Particularly interesting is his analysis of the number
of notes in musical scales. Von Hoerner suggested that the
use of a 12-tone scale in Western music is not completely
arbitrary. Rather, this number of notes yields one of only a
handful of possibilities for a workable foundation for
polyphonic music. Specifically, polyphonic music must
meet two competing demands, which always entails a
compromise. First, an octave needs to be divisible into
equal parts to allow for modulations from one key to
another. Second, the tones corresponding to these divi-
sions should have harmonic frequency ratios to one
another. Any attempt to satisfy both of these conditions,
however, requires some compromise. Equal intervals do
not provide exactly harmonic tones, thus one must be
content with relatively close matches that use only some
of all possible harmonics. For example, classical Western
music uses a 12-tone scale that allows for 5 harmonics.
But according to von Hoerner, a 12-tone scale does not
exhaust the ‘‘good compromises’’ for polyphonic music.
One might also use a 31-tone scale or a 5-tone scale. The
choice among these scales might provide a clue about the
sensory functioning of the intelligence using these scales.
Those beings with more sensitive auditory processing
than humans might make use of the finer divisions of the
31-tone scale. In contrast, extraterrestrials with less
sensitive auditory systems may be more likely to use a
mere 5 tones. While the choice between scales may not be
dictated by biology (as suggested by the existence of 5-
tone, 12-tone, and 31-tone scales among human cultures),
sensory apparatus may sometimes restrict the range of a
species’ musical scales.
3. A didactic approach
As noted above, the recordings onboard the Voyager
spacecraft included musical selections, which were drawn
from a range of terrestrial cultures. The hope of the
recordings’ creators was that the structure of the music
might be intelligible to extraterrestrials because of
universal characteristics of the music. The present paper
assumes a more skeptical stance and suggests that music
as experienced by humans may need to be taught in order
to be intelligible to extraterrestrials.
Previous proposals for interstellar messages have sug-
gested beginning a message with a primer based on basic
mathematics and science, which any civilization capable of
radio communication is anticipated to have in common
with us [1,2,4]. Similarly, one could start to communicate
terrestrial ideas about music by initially presenting an
essential ‘‘vocabulary’’ and ‘‘syntax’’ of music. There are
many possible ways to construct such introductory primers,
in part dependent on what are assumed to be the as the
essential elements of musical expression. For example, to
describe some of our notions of music, we might commu-
nicate features such as pitch, dynamics, tone color, and
duration. Such a tutorial might initially isolate individual
components of musical expression in a somewhat artificial
manner, only later introducing their complex interactions
as heard in fully developed music.
In most discussions of interstellar messages, one of the
most fundamental differences between the interstellar
composition and traditional forms of art created for
human audiences is overlooked. The actual physical
medium of radio waves through which interstellar
messages are conveyed is at frequencies beyond the range
of human sight or hearing. In contrast, the medium of
traditional art is directly perceptible to humans. While the
signals bearing interstellar messages can be transduced
into a range that is perceptible to humans, in their raw
forms, such signals are invisible, inaudible, and intangible
to a human audience.
Although the electromagnetic signals used to convey
interstellar music may be imperceptible to beings on
either end, nevertheless, aspects of music can be conveyed
very directly in physical properties of the signals that can
be measured accurately by instrumentation. For example,
like music, interstellar signals are of a specific frequency
that can vary over time. If desired, such signals could be
modulated, directly conveying our notions of rhythm and
melody, ‘‘for example, if we want to communicate some-
thing about rhythm, we should rhythmically vary the
signal itself’’ [11].
4. Cognitive modeling
Messages using this didactic approach can be based on
an expressly cognitive model of human music perception,
D.A. Vakoch / Acta Astronautica 67 (2010) 1406–1409 1407
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which has several advantages: a cognitive model is
empirically testable, it may be linked to parallel messages
providing an account of human perception and cognition,
and it provides multiple levels at which decryption might
occur [6]. By illustrating progressively more complex
rules that specify how terrestrial musical melodies are
generated, and by doing so through radio signals that
directly mimic these melodies, extraterrestrials are pre-
sented with two means of understanding human music
perception. First, extraterrestrials may be able to com-
prehend the musical content we attempt to convey,
because they can follow our intended ‘‘chain of reason-
ing,’’ or in this case, the ‘‘musical tutorial.’’ However, if
they cannot comprehend this content as an artistic
expression, they may still be able to infer something
about our cognitive and perceptual systems based on the
patterning of the message we send. Thus, even without
comprehending the musical intent of such a message, the
recipients might gain some understanding of human
information-processing capabilities, because we are pro-
viding a message that is meant to describe our cognitive
processes, by making the form of the message reflect
these capabilities. This is an extension of the author’s
earlier proposal that the form of the message should
reflect its meaning [9].
5. A direct approach
Some of the structural characteristics of music – temporal
modulations of transmissions at precise frequencies – can be
used to communicate basic scientific information [7].One
critique of prior suggestions for interstellar messages is that
these messages often rely on conventions of representation
that may be unique to a single species’ model of the physical
universe. This criticism does not call into question the actual
existence of physical reality. Rather, it points out that one
species’ conceptualizations and theoretical models about
reality may not necessarily be readily comprehensible by a
species relying on very different models—even though the
two species may be studying the same underlying reality
[10]. For instance, pictorial representations of atoms might
rely on the Bohr model, in which electrons circle the atom’s
nucleus much like planets orbit a star. Nevertheless, this is
only one way of representing atomic structure, and it is not
immediately obvious that even other species with advanced
knowledge of chemistry will use models that are directly
commensurable with ours [9].
One potential solution to the above problem would be
to attempt to communicate our concepts of chemistry
through signals that directly mimic physical phenomena
related to the chemical concepts we are conveying [7]. For
example, one might transmit electromagnetic signals at
frequencies corresponding to some subset of those
spectral lines that are uniquely associated with energy
emissions from certain chemical elements. Thus, a
hydrogen atom might be represented more directly by
signaling at some of the frequencies at which this element
naturally emits. These frequencies may be rather far
from each another, so the actual process of transmission
might involve starting with a single frequency and slowly
drifting the signal to another frequency associated with
the emission spectrum of that element. Following this
approach, one could transmit for awhile at each frequency
of a characteristic emission line, then move on to the next
target frequency until each has been transmitted. Given
the wide range of frequencies accessible to some radio
telescopes, a significant range of chemical concepts could
be communicated in this manner. For example, the SETI
Institute’s Allen Telescope Array covers a range of 4.5
octaves, with frequencies ranging between 0.5 and
11.2 GHz.
Once we are able to convey individual chemical
constituents, we might then describe the process by
which these constituents combine to form more complex
molecules. Since the early days of the search for extra-
terrestrial intelligence (SETI), astronomers have suggested
searching at or near frequencies associated with strong
emission lines of the constituents of water—hydrogen
(H
+
) and hydroxyl (OH
). Although frequencies asso-
ciated with hydrogen and hydroxyl emission spectra have
often been suggested as ‘‘magic frequencies’’ to help
narrow searches – with some advocating searches within
the ‘‘water hole’’ that spans the range of frequencies
between 1420 and 1640 MHz – others have not suggested
using these frequencies as icons of the constituents
themselves.
To see how we might represent iconically the chemical
equation H
+
+OH
-H
2
O in an interstellar message, con-
sider Fig. 1. At the left side of the figure, a transmission at
or near the hydrogen line (1420MHz) appears, and as time
passes (moving from left to right in the figure), this first
signal is joined by another signal sent at the frequency
associated with the strongest hydroxyl line (1640 MHz).
After each of these two signals is well established,
additional signals slowly drift away from the hydrogen
and hydroxyl lines, combining at the frequency associated
with the 22GHz water maser line. The intended message is
that hydrogen and hydroxyl combine to form water.
As an alternative to the transmission represented in
Fig. 1, one might simply have the transmissions at 1420
and 1640 MHz end, and immediately begin a transmission
at 22 GHz. Given rapid advances in technology, it is
Fig. 1. An iconic interstellar message representing the combination of
hydrogen and hydroxyl to form water (H
+
+OH
-H
2
O).
D.A. Vakoch / Acta Astronautica 67 (2010) 1406–14091408
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reasonable to assume that this entire range of frequencies
could be detected by even rudimentary technological
civilizations with radio telescopes. For example, a modest
expansion of the existing Allen Telescope Array would
make narrowband signals detectable within this entire
frequency range.
A process analogous to that used to describe chemical
concepts could also be used to communicate musical
concepts. Though the initial form of the message might
focus on basic parameters of music, eventually one might
transmit at multiple frequencies, creating a sort of
‘‘interstellar symphony’’ [8], with the frequencies of the
signals having the kind of relationship to one another
identified by von Hoerner for well-tempered polyphonic
music. This approach would mark a significant shift from
the traditional approach that messages should be encoded
in a form that bears no direct relationship to the content
of the message. While the traditional procedure may be
efficient from an information theoretic perspective, it
does not take into account that the process of decoding
such messages may be significantly more challenging
than typically anticipated.
As noted above, the particular form of the musical
tutorial might provide information about the cognitive
functioning of a species [6]. For instance, Narmour has
posited that as humans begin to hear even very few notes
played sequentially, they begin to form strong anticipa-
tions of the sort of tones that are likely to follow [5]. One
of the parameters that influence these anticipations is the
size of the intervals between notes (from a relatively small
interval—yielding notes ‘‘close together,’’ to relatively
large intervals—resulting in notes ‘‘far apart’’). Similarly,
the parameter of direction of pitch (increasing, decreasing,
or remaining stable) can create expectations about
subsequent notes.
By structuring a musical primer to reflect such
‘‘cognitive primitives’’ of music perception as interval size
and pitch direction, one could introduce a basic vocabulary
that reflects both components of music and parameters of
human auditory perception. By conveying this information
directly in the form of the electromagnetic signal, clues
would be provided about our intended meaning as well as
about the senders of the message, all in a form that may be
more intelligible than many previously proposed formats
for interstellar communication.
Acknowledgments
The author gratefully acknowledges the following
support of this research: The John Templeton Foundation,
though its Grant #1840, ‘‘Construction of Interstellar
Messages Describing the Evolution of Altruistic Behavior;’’
President Joseph Subbiondo, Academic Vice President
Judie Wexler, and Clinical Psychology Department Chair
Katie McGovern of the California Institute of Integral
Studies for sabbatical and ongoing research leaves; CEO
Thomas Pierson and Director of SETI Research Jill Tarter of
the SETI Institute for support of research on SETI and
Society; and Jamie Baswell, as well as Harry and Joyce
Letaw, for financial support through the SETI Institute’s
Adopt a Scientist program.
References
[1] C.L. DeVito, Languages, science and the search for extraterrestrial
intelligence, Leonardo 25 (1992) 13–16.
[2] H. Freudenthal, Lincos: Design of a Language for Cosmic Inter-
course; Part I, North-Holland, Amsterdam, 1960.
[3] J. Knowlson, Universal Language Schemes in England and France
1600–1800, University of Toronto Press, Toronto, 1975.
[4] P. Morrison, Interstellar communication, in: A.G.W. Cameron (Ed.),
Interstellar Communication: A Collection of Reprints and Original
Contributions, W. A. Benjamin, New York, 1963.
[5] E. Narmour, The Analysis and Cognition of Basic Melodic Structures:
The Implication-Realization Model, University of Chicago Press,
Chicago, 1990.
[6] D.A. Vakoch, Cognitive modeling of music perception as a founda-
tion for interstellar message composition. Paper IAA-00-IAA.9.2.10
presented at the SETI: Interdisciplinary Connections Review Meet-
ing, 51st International Astronautical Congress, Rio de Janeiro, Brasil,
October 2000.
[7] D.A. Vakoch, An iconic approach to communicating chemical
concepts to extraterrestrials, SPIE Proceedings 2704 (1996) 140–149.
[8] D.A. Vakoch, The music of the spheres, Sky & Space 11 (3) (1998) 24.
[9] D.A. Vakoch, Signs of life beyond Earth: a semiotic analysis of
interstellar messages, Leonardo 31 (1998) 313–319.
[10] D.A. Vakoch, Technology as a manifestation of intelligence: does
shared technology imply shared science and mathematics?
[Abstract.], Astrobiology 8 (2) (2008) 391.
[11] D.A. Vakoch, To the stars, silently, Leonardo 37 (2004) 265.
[12] S. von Hoerner, Universal music?, Psychology of Music 2 (1974) 18–28.
D.A. Vakoch / Acta Astronautica 67 (2010) 1406–1409 1409
