The origins of music in auditory scene analysis and the roles of evolution and culture in musical creation

Abstract

Whether music was an evolutionary adaptation that conferred survival advantages or a cultural creation has generated much debate. Consistent with an evolutionary hypothesis, music is unique to humans, emerges early in development and is universal across societies. However, the adaptive benefit of music is far from obvious. Music is highly flexible, generative and changes rapidly over time, consistent with a cultural creation hypothesis. In this paper, it is proposed that much of musical pitch and timing structure adapted to preexisting features of auditory processing that evolved for auditory scene analysis (ASA). Thus, music may have emerged initially as a cultural creation made possible by preexisting adaptations for ASA. However, some aspects of music, such as its emotional and social power, may have subsequently proved beneficial for survival and led to adaptations that enhanced musical behaviour. Ontogenetic and phylogenetic evidence is considered in this regard. In particular, enhanced auditory-motor pathways in humans that enable movement entrainment to music and consequent increases in social cohesion, and pathways enabling music to affect reward centres in the brain should be investigated as possible musical adaptations. It is concluded that the origins of music are complex and probably involved exaptation, cultural creation and evolutionary adaptation.

Keywords: auditory scene analysis; entrainment; evolution; metre; music; pitch.

Figure 1.

Harmonic structure and determining the number of auditory objects with simultaneous sound inputs. (A) A complex tone with fundamental frequency (f₀) at 200 Hz and harmonics at integer multiples of f₀, which is perceived as a single tone (auditory object) with a pitch of 200 Hz. (B) Two complex tones (sound sources) with f₀s at 200 and 260 Hz and their harmonics. It can be seen that their harmonics overlap in frequency range, so when they simultaneously impinge on the ear, the auditory system must decompose the incoming sound into its frequency components and use its knowledge of harmonic structure to recombine them into representations of the original sound sources. (C) That the brain uses harmonicity to determine the number of auditory objects can be seen by mistuning one harmonic of the 200 Hz complex tone shown in (A). In this case, two tones are heard. The mistuned harmonic is heard as one auditory object and the remaining components, which are all integer multiples of f₀, fuse into a second auditory object. (D) Pitch of the missing fundamental: the brain creates the sensation of pitch as can be seen in that when f₀ is removed from a complex tone stimulus, the perceived pitch remains at f₀.

Figure 2.

The effects of pitch proximity and tempo on determining the number of auditory objects in sequential streams of sounds. (A) When a higher tone repeats at a regular interval and a lower tone repeats at half the tempo of the higher tone, and they are arranged as in (A), all of the tones are perceived to come from a single sound source (as depicted by the dotted lines) and a gallop rhythm is heard. (B) When the higher and lower tones are sufficiently separated in frequency, they can no longer be integrated into a single stream. Two auditory objects are heard, one a repeating high tone and one a repeating low tone, and no gallop rhythm is perceived. This demonstrates that the auditory system expects a single sound source to remain reasonably consistent in pitch. (C) When the tempo of the sequence in (B) is slowed down, again the two pitches can be integrated into a single auditory object, and the gallop rhythm is heard again, consistent with the idea that the auditory system expects an auditory object to change pitch slowly. (Adapted from [41].)