Impaired perception of harmonic complexity in congenital amusia: a case study

This study investigates whether congenital amusia (an inability to perceive music from birth) also impairs the perception of musical qualities that do not rely on fine-grained pitch discrimination. We established that G.G. (64-year-old male, age-typical hearing) met the criteria of congenital amusia and demonstrated music-specific deficits (e.g., language processing, intonation, prosody, fine-grained pitch processing, pitch discrimination, identification of discrepant tones and direction of pitch for tones in a series, pitch discrimination within scale segments, predictability of tone sequences, recognition versus knowing memory for melodies, and short-term memory for melodies). Next, we conducted tests of tonal fusion, harmonic complexity, and affect perception: recognizing timbre, assessing consonance and dissonance, and recognizing musical affect from harmony. G.G. displayed relatively unimpaired perception and production of environmental sounds, prosody, and emotion conveyed by speech compared with impaired fine-grained pitch perception, tonal sequence discrimination, and melody recognition. Importantly, G.G. could not perform tests of tonal fusion that do not rely on pitch discrimination: He could not distinguish concurrent notes, timbre, consonance/dissonance, simultaneous notes, and musical affect. Results indicate at least three distinct problems-one with pitch discrimination, one with harmonic simultaneity, and one with musical affect-and each has distinct consequences for music perception.