The co-occurrence of pitch and rhythm disorders in congenital amusia.

The most studied form of congenital amusia is characterized by a difficulty with detecting pitch anomalies in melodies, also referred to as pitch deafness. Here, we tested for the presence of associated deficits in rhythm processing, beat in particular, in pitch deafness. In Experiment 1, participants performed beat perception and production tasks with musical excerpts of various genres. The results show a beat finding disorder in six of the ten assessed pitch-deaf participants. In order to remove a putative interference of pitch variations with beat extraction, the same participants were tested with percussive rhythms in Experiment 2 and showed a similar impairment. Furthermore, musical pitch and beat processing abilities were correlated. These new results highlight the tight connection between melody and rhythm in music processing that can nevertheless dissociate in some individuals.