Listening to a good symphony orchestra in your favorite concert hall, concentrate first on the violins. Now focus your attention on the clarinets, then the percussion section. Next listen to a male quartet and single out the first tenor, the baritone, the bass. This is a very remarkable power of the human ear/brain combination. In the ear canal, all these sounds are mixed together; how does the ear succeed in separating them? The sea surface might be disturbed by many wave systems, one due to local wind, one from a distant storm, and several wakes from passing vessels. The eye cannot separate these, but this is essentially what the ear is constantly doing with complex sound waves. By rigorous training, a keen observer can listen to the sound of a violin and pick out the various overtones
apart from the fundamental!
From THE MASTER HANDBOOK OF ACOUSTICS 3rd Edition by F. Alton Everest