Acoustic Processing and the Origin of Human Vocal Communication

Humans have inherited from their remotest mammalian ancestors an integration of the sensory and motor systems that permits the exchange of signals and information, led by an instinctive response to harmonicity. The transition, from capacity for animal communication involving calls, facial expression and gestures, to modern human culture that embraces language, music, and dance, has resulted from anatomical adaptations such as upright posture, a distinct oro-facial and respiratory tract arrangement, and important changes in neural architecture, connectivity and plasticity. A key development on which modern human vocal abilities depend was the achievement of a feedback loop between the perception and production of voiced sound that allows precise matching, imitation, and meaningful variation, of the acoustic properties: fundamental frequency, duration, amplitude, and timbre; all contributing to the capacity to coordinate simultaneous participation. These are the four specific properties that influence our sensations of sound. They play parallel and complementary roles in both language and vocal music, represented in blended synchrony such as unison song and collective speech as well as temporally organised and coordinated sequences such as call-and-response and polyphony. In turn, responding especially to the properties of the Harmonic Series, such features inform the musical employment of tools – musical instruments – that make use of materials available in the local environment (skin, bone, stone, bamboo, wood, etc.) to provide increased range and loudness as well as alternative timbres to those produced by the voice. We propose a framework by which the adaptations essential to such universal behaviours may have arisen, drawing on an extensive and varied literature to explore the potential of this position for illuminating the nature of human musicality and its relationship to language development.