An in-depth examination of numerous unprompted musical displays by a captive male chimpanzee, identified as Ayumu, suggests that the primate’s consistent temporal patterns and discernible ‘play face’ could offer insights into how early human ancestors transitioned vocal emotions into instrumental auditory expressions.
Ayumu the chimpanzee spontaneously produced long, multicomponent instrumental displays by drumming, dragging, and throwing self-detached objects. Transition and rhythm analyses revealed non-random sequencing partially resembling pant-hoot structure, predominantly isochronous timing, and a more stable tempo when using tools than with the body. Accompanying play-face and silent bared teeth expressions suggest high arousal and positive affect, supporting the idea that affective vocal expression can be externalized through instrumental sound. Image credit: Hattori et al., doi: 10.1111/nyas.70239.
In February of 2023, Ayumu, a 26-year-old male chimpanzee housed at Kyoto University’s Center for the Evolutionary Origins of Human Behavior, unexpectedly presented researchers with a spontaneous musical demonstration.
He proceeded to detach floorboards from a walkway and utilize them as percussive instruments, generating intricate, structured sonics that bore resemblance to vocal pronouncements.
“The drumming capabilities of Ayumu are certainly not unprecedented,” indicated Dr. Yuko Hattori and her colleagues from Kyoto University.
“It is widely recognized that chimpanzees engage in instrumental behaviors, and they exhibit particular proficiency in drumming activities.”
“However, on this particular occasion, Ayumu’s integrated performance of drumming and vocalizations—encompassing a variety of rhythmic constituents—represented a wholly novel occurrence.”
Over the period spanning February 2023 to March 2025, the research team documented a cumulative total of 89 spontaneous performances by Ayumu.
These recorded instances detailed the methodology by which he detached floorboards from a walkway and employed them as implements to create audible presentations.
“It was profoundly fascinating for me to observe the manner in which the chimpanzee utilized tools to elicit diverse sound patterns concurrently with the articulation of a vocal display,” stated Dr. Hattori.
Leveraging Ayumu’s performances, the investigators sought to ascertain if vocal expressions could be transmuted into instrumental sonic output.
Their investigative approach commenced with an assessment of his behavioral repertoire, dissecting it into discrete actions such as striking, dragging, and propulsion.
Subsequently, the connections between these individual components were evaluated through transition analysis, which served to differentiate between chance occurrences and deliberate sequences.
The final phase involved an analysis of the temporal intervals between percussive impacts and a comparison of the rhythmic consistency achieved through tool utilization versus drumming executed with the limbs.
The analytical findings indicated that the sequence of sounds produced via the tools was not random in nature, and that the inter-strike intervals were isochronous—maintaining a uniform tempo, akin to a metronomic beat.
In practice, the employment of tools resulted in a more consistent rhythm than that achieved by using only the hands or feet.
Furthermore, the scientists observed accompanying facial expressions, notably the ‘play face,’ which is generally indicative of playful engagement and suggests positive emotional states.
Such expressive facial cues are not typically documented in vocalizations, positing that emotional signals previously conveyed through vocal means might have been externalized and evolved into tool-generated sounds.
“Ayumu’s demonstrations provide compelling evidence that non-human primates are also capable of outwardly expressing vocal-analogous signals through the use of instruments,” the authors concluded.
“Our forthcoming research interests lie in analyzing the responses of other chimpanzees and the influence of Ayumu’s displays within his social cohort.”
This investigation has been formally published in the Annals of the New York Academy of Sciences.
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Yuko Hattori et al. 2026. Combinatorial Instrumental Sound-Making in a Captive Chimpanzee: Evolution of Vocal Externalization. Annals of the New York Academy of Sciences 1557 (1): e70239; doi: 10.1111/nyas.70239
