A fruitful way to talk about voice in writing is to heighten the magical dimension. That is, even though we know magic isn't real, poetry itself is magical language. It is trying consciously to get sound and rhythm in--something other than mere semiosis or meaning. Someone said that prose is for communication, poetry for communion.
In effect, I am trying to get more leverage in my investigations of voice in writing. Till now I have tended to try to get as clear and precise and rational as I can in talking about voice--especially since I sometimes get accused of being too irrational or obscure. But after doing some writing in the sensible mode, it strikes me that perhaps it would be helpful to grasp the nettle and come at it the other way--and say things like this: When writing has voice, it simply seems magical; it fools you into thinking that it carries some of the essence of the writer or that it is "authentically" related to the core of the real person who wrote it.
We can simply just grab right ahold of that empirical fact about the effects of texts on persons and acknowledge that of course language functions or seems to behave like magic sometimes. Indeed language is always trying~ to burst out of its rational semiotic mode. An example: much of academic writing is magical or talismanic: people "always already" try to use the phrases and tones and rhythms of the powerful people to latch on to some of the juice of the great deconstructive fathers.
So we can be perfectly rational and sensible--like anthropologists and linguists and simply try to understand the magical dimension of language. And, of course, it turns out that people have been thinking about language as magic for a long time and we can see what they have to say. One prime example, I gather, is Plato's Cratylus.