I'm far from a musical expert, but I thought this was essentially how many instruments work: Each string/hole/whatever produces a different resonant frequency which is orthogonal from the others the instrument produces; therefore any combination of strings/holes/whatevers creates a sound that cannot be created by any other combination of strings/holes/whatevers.
Please, correct me if I'm wrong.
Edit (before someone nitpicks, I'll do it!): I'm aware interacting with instruments doesn't produce _only_ resonant frequencies; and that the off-resonance is what gives an instrument its characteristic sound, even when playing the same note as a different instrument.
Please, correct me if I'm wrong.
Edit (before someone nitpicks, I'll do it!): I'm aware interacting with instruments doesn't produce _only_ resonant frequencies; and that the off-resonance is what gives an instrument its characteristic sound, even when playing the same note as a different instrument.