  Multi-pitch perception is investigated in a listening test using 30
recordings of musical sounds with two tones played simultaneously, except for
two gong sounds with inharmonic overtone spectrum, judging roughness and
separateness as the ability to tell the two tones in each recording apart. 13
sounds were from a Western guitar playing all 13 intervals in one octave, the
other sounds were mainly from non-Western instruments comparing familiar with
unfamiliar instrument sounds for Western listeners. Additionally the sounds
were processed in a cochlear model transferring the mechanical basilar membrane
motion into neural spikes followed by a post-processing simulating different
degrees of coincidence detection. Separateness perception showed a clear
distinction between familiar and unfamiliar sounds, while roughness perception
did not. By correlating perception with simulation different perception
strategies were found. Familiar sounds correlated strongly positive with high
degrees of coincidence detection, where only 3-5 periodicities were left, while
unfamiliar sounds correlated with low coincidence levels. This corresponds to
an attention to pitch and timbre respectively. Additionally, separateness
perception shows an opposite correlation between perception and neural
correlates between familiar and unfamiliar sounds. This correlates with the
perceptional finding of the distinction between familiar and unfamiliar sounds
with separateness.
