Thus we can safely say that although sounds have birth and death, the hearing capacity does not. It actually never vanishes. All existence, including dharmas, is impermanent and therefore subject to birth and death - just like magic, like bubbles or like shadows. The nature of hearing, on the other hand, can never be destroyed. In that manner we come to know the bright and accomplished nature of hearing.
Nature is the substance, mind, the function.
The function never separates from the substance, nor the substance from the function. Function and substance, though separate, are causally connected. Although both retain their own character, they are inseparable. Dharma practice can start right at this point. One needs to understand one's mind, see one's True Nature and following that, attain the Tao.