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Abstract:
A melody consists of a temporal sequence of pitches. Its ‘Gestalt’ is invariant to absolute pitch but depends on the relation between pitches [[unable to display character: –]] the relative pitch profile. Consequently, a melody can be recognised regardless of the instrument used to play it and it even retains its identity after transposition to a different key, which involves a global change of all pitches in the melodic sequence. In contrast, a change in a melody’s temporal pitch order is usually accompanied with a change in its relative pitch profile and therefore also affects its melodic ‘Gestalt’.
Pitch processing is assumed to occur in the auditory cortex. It is however still unknown whether early auditory regions are capable of integrating pitches over time and whether the resulting representations are invariant with respect to the key of their presentation. Here, we exposed participants to different melodies composed of the same four harmonic pitches during fMRI recordings. Additionally, we presented the same melodies transposed to different keys or played on different instruments.
We found that melodies were invariantly represented by their BOLD activation patterns in primary and secondary auditory cortices across instruments, and also across keys. Our findings extend common hierarchical models of auditory processing by showing that melodies are encoded independent of absolute pitch and based on their relative pitch profile as early as primary auditory cortex.
