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Musical analysis of calls: Using the vocal repertoire for tamarins (Cleveland & Snowdon 1982)
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along with more recent recordings of tamarin calls, DT analyzed the structure of calls to
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determine which call types would be classified similarly based on musical components. He
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subsequently asked five professional musicians to evaluate the same calls with playback slowed
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down to bring pitch and tempo within the range of human music. Each musician plays a different
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instrument and was unaware of the premises of this study. They were also unaware of call
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context when evaluating structure. There was a clear consensus among all of the musicians. CTS
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provided the contexts in which each call type was used after the structural classification had been
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completed.
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Musical Analysis of Tamarin Vocalisations
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Snowdon & Teie Supplemental Materials
Natural human tempos range from slow breathing (18/min.) to the footfalls of running
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(340/min.) and all the tempos of our music fall within that range (40-208 beats per minute), the
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intermediate tempos of heartbeats and walking being the most common. A normal human’s
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vocal range spans approximately two octaves, ranging from 65 to 262 Hz for a low-voiced man,
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to 294 to 1175 for a high-voiced woman. The monomorphic tamarin displays a vocal range
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spanning nearly 5 octaves from 262 to 7040 Hz. Most tamarin vocalisations are approximately
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eight times faster than and three octaves above the range of comparable female human affiliation
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vocalisations. Many tamarin calls displayed clear chordal structures with key centers on a
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diatonic scale. Tritones, minor seconds, noise and short staccato notes were more common in
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calls relating to fear and threat. The pitch variations and aspirant onsets of tamarin vocalisations
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are from two to three times faster than human vocalisations.
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We identified five clusters of call types: Cluster 1 included Small Initially Modulated
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Whistle, Terminally Modulated Whistle, Ascending Multi Whistle and the Partial Quiet Long
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Call. (Call names from Cleveland & Snowdon 1982, Campbell & Snowdon 2007) These calls
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had a narrow frequency range (1.9 to 3.2 kHz related to “head voice” or falsetto as with human
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infant directed calls) with relatively long notes ranging from 150 to 500 ms and ascending notes
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at intervals of 2nds, 3rds and 4ths of the first note. The structures were simple with 2-4 notes per
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call. Each of these calls is used in contexts of affiliation and positive social interaction.
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Cluster 2 consisted of Type A and Type H chirps and Hooked Chatter. All contained
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short notes of descending intervals of 3rds, 4ths, 5ths, and 6ths. Frequencies ranged from 3.2 to 9.4
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kHz and were also in a “head voice”. The repeated notes were given at 6-8 notes per s. All of
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these calls are given in contexts of high arousal or in response to threats.
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Cluster 3 consisted of Chevron Chatter and Type E Chirp Chatter. These calls contain
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motives that begin and end on the same pitch with an interval of a major second in between. The
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notes are produced in staccato rhythm at 12-14 notes per second. Both calls are used in contexts
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of high fear and high arousal.
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Cluster 4 consisted of Type F- chirp + Whistles, Normal Long Calls and Large
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Modulated Multi-Whistles. These are full-voiced (normal-voiced) calls ranging from 1.1 to 2.35
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kHz with note durations of 200-1100 ms with 2-4 notes per call. All have rising pitches with no
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slowly descending slides. The first two calls are vocal responses to hearing the calls of an
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unfamiliar group and the last is given in aggressive play with the broad context of all of the calls
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being confident threat.
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Cluster 5 calls were the only ones that contained triple meters (note, note, silence). The
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Rapid Whistle contained ascending intervals in 3rds and 4ths. Notes were approximately 100 ms
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duration with 3-4 notes per call with a frequency range of 0.4 to 1.4 kHz. This call is used by
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young animals in play mounting and by adults before sex. The Type B Trill has repeated
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descending intervals of thirds with a frequency range from 1.6 to 3.2 kHz and is used in
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retrieving infants, so both calls are used in contexts of approach.
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These analyses were used to develop the principles for the composition of tamarin based
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music summarised in Supplemental Table 1.
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Affiliation vocalisation-based music: A selection from Barber’s “Adagio for Strings” was used
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as a human-based control. It contained 40 notes/min, and frequencies ranged from 82 to 622 Hz
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which correspond to the tempo and low frequency range of human moans. Of the 26 pitch
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movements in the melody, 21 moved in stepwise motion and the other 5 were descending minor
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thirds, intervals that mimic the melodic contours of moaning. The timbre of the Adagio was
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relatively pure (string instruments have a wide range of timbres available, and those used in this
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recording are fairly pure wave-form sounds). The second piece was an excerpt from “The
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Fragile” by Nine Inch Nails. This excerpt contained the relatively pure waveform sounds of a
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softly played solo piano. The pitches changed at a rate of 35 notes per minute in regular rhythm.
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The music consisted of two simultaneous lines. The frequencies of the melodic line ranged from
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196 to 587 Hz while the bass line frequencies range from 73 to 98 Hz. The two lines moved
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primarily in contrary motion with a descending melodic line (in the range of an adult female
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voice) accompanied by an ascending bass line (in the frequency range of an adult male voice).
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The four-note ascending scale in the bass was repeated 4 times, providing the accompaniment for
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4 sentence-length melodic phrases.
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The first tamarin affiliative vocalisation based music sample contained 52 notes per
minute, approximating the rate of frequency variation in the normal long call and affiliation calls
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with frequencies ranging from 1.9 to 3.7 kHz. This piece was designed to capture the quality of
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the pure, high sounds common to the range and timbre of tamarin affiliation vocalisations. It was
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written in ABA form and played on the ‘cello using the technique of artificial harmonics which
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produced a pure flute-like quality. It was constructed entirely of motivic pairs, since the most
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easily perceived pattern in music is the immediately repeated pattern and most mammalian
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vocalisations consist of repeated calls. All motives were either two or four note motives in
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regular rhythms in keeping with observed intragroup tamarin vocalisations that tended to consist
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of two, four, and eight note groups in regular rhythms. Most motives were descending to mimic
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the descending frequencies of calming vocalisations used by humans to control behaviour in
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working animals.
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The A section of the second tamarin affiliation piece in B flat consisted of two
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simultaneously sounding lines of artificial harmonics on the ‘cello. One line was similar to the
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melody from the first piece and the second line included a musical representation of the rising
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frequency with diminishing amplitude motive common to affiliative tamarin vocalisations. The B
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section of introduced a lowered sixth into the tonality and a drum-like pulse was created by
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thumping the cello body with the thumb. The tamarin heart rate was used as a basis for the tempo
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of this pulse.
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Fear/threat vocalisation-based music: We used an instrumental excerpt from “Of Wolf and
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Man” by Metallica as one human based example of arousing music. The sonic characteristics of
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this music include a strong bass and an enhanced broadband timbre similar to that found in
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human fear/threat vocalisations in a fast march tempo (120 beats per minute) and a minor
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modality, frequently using dissonant intervals of minor seconds and the tritone. The second
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piece was an excerpt from “The Grudge” by Tool. This excerpt contained pitch changes at the
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rate of 81 per minute. The frequencies of the bass line range from 73 to 147 Hz and the upper
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line ranges from 220 to 262 Hz. Two guitars play repeated motives consisting of minor seconds
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and thirds using quick-onset picked notes in moderately complex timbre accompanied by
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simultaneously rhythmic pedal bass drum and tom-toms.
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The first tamarin threat vocalisation based music was constructed in ABA form. The A
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section evokes the complex, broad band timbre of threats played on the ‘cello sul ponticello
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(bowing near the bridge to add harshness to the sound) in a fast tempo (554 beats per minute)
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with ascending pitch crescendo motives that bear a musical similarity to the ascending pitch
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crescendo motives found in fear/threat calls. These were accompanied by an underlying
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irregular rhythmic unvocalised aspirant “ch”, also a broad band timbre. The B section had two
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lines of music, each consisting only of the notes B flat and B natural (7.5 and 7.9 kHz), creating
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quickly alternating unison – minor second intervals. The second piece was based on three
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elements of mobbing vocalisations: quick, descending intervals, long, broadband sounds, and
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antiphonal, chorused calls that are often used when perceived threat is present. The form was
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AbbABBCABB where the second, third, and fourth statements of the B section were augmented
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with a countermelody that, combined with the original melody, created dissonant harmonies.
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The broad band timbre of the theme area in the B section was created with a rapid repetition of
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bow strokes (tremolo) which is commonly found in “agitato” classical music. The modality of A
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harmonic minor was introduced in the opening figure and in the first two notes in the B theme,
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and then the dissonant D sharp dominated the melodic contour of the section. The C section was
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based on quickly repeated notes and was comprised of four different lines, two of them with
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added tritone double stops. The ascending crescendo motive became gradually higher and louder
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and the intervals between the repetitions of the motive were shortened as seen in spontaneous
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fear/threat calls of many animals (e.g. Schecha et al. 2007).
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References
Campbell, M. W. & Snowdon, C. T. 2007 Vocal response of captive-reared Saguinus oedipus
during mobbing, Int J Primatol 28, 257-270.
Cleveland, J. & Snowdon C,T. 1982 The complex vocal repertoire of the adult cotton-top
tamarin (Saguinus oedipus). Z Tierpsychol 58: 231-270.
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Schehka, S., Esser, K.-H. & Zimmermann, E. 2007 Acoustical expression of arousal in conflict
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situations in tree shrews (Tupaia belangeri). J. Comp. Physiol. A 193, 845-852.
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Supplemental Table 1
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Frequency range Hz Notes per minute
Timbre
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Affiliative Based Music
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Human 1
82-622
40
Pure Tone
129
Human 2
196-587
35
Pure Tone
130
Tamarin 1
1900-3700
52
Pure Whistle
131
Tamarin 2
1800-4100
82
Pure Whistle
132
Threat Based Music
133
Human 1
82-124
206
Harsh/Noisy
134
Human 2
73-262
307
Harsh/Noisy
135
Tamarin 1
1400-7900
554
Harsh/Noisy
136
Tamarin 2
1300-5400
496
Harsh/Noisy