There are two aspects of vibrations; fine and gross; both, containing, varied degrees. Some are perceived by the soul, some by the mind, and some by the eyes. What the soul perceives are of the feelings; what the mind conceives of are the thoughts; what the eyes see are the vibrations solidified from their ethereal state, and turned into atoms, which appear in the physical world, constituting the elements; ether, air, fire, water and earth. The finest vibrations are imperceptible even to the soul. The soul itself is formed of these vibrations; it is their activity, what makes it conscious.
Inayat Khan, Mysticism of Sound