Neuroscientists subjected volunteers with amusia -- difficulty telling different melodies apart and remembering simple tunes -- to shifts in pitch comparable to those that occur when someone plays one piano key and then another  The volunteers were unable to discern a difference between the tones
But the volunteers were able to track timed sequences of musical tones and perceive slight changes in timing
Amusia results more from an inability to discern pitch than from an inability to discern timing.