The two most common frames of reference seem to be (1) agency attribution at the level of sentence structure (active vs. passive voice) and (2) the use of stylistic elements to stamp the persona of the author(and/or a character) with identity characteristics- this is closely related to the idea of point of view (POV).
Complexities emerge when we look more closely at (2), since "voice" is used in all kinds of more-or-less metaphorical ways. To refer to Dorothy Sayers' "dry voice" is to say something about her outlook as well as her writing style. "Voice is also associated with direct quotation, which may or may not include dialect or style markers that flesh out social identity, i.e. the "Black voice" of Jim, the formerly enslaved character in Huckleberry Finn is based in speech patterns that Twain may have heard and studied. "Voice" is also associated with individual as well as collective perspectives of a more general nature. One could describe Questlove's recent film Summer of Soul (which is about the Harlem Cultural Festival of 1969) as simultaneously showcasing Black voices and as redeeming the erasure of "the Black voice" from the mainstream cultural history of the 1960s.
So, is there a common thread to these different ways fo referring "voice" in written language? What is it? Are there other ways of using "voice" that I haven't mentioned?
I'd be especially interested in perspectives from rhetoric, since there seem to be several implicit distinctions and variables in play, and I could use some help in parsing them out.
There's a useful thread What does voice in writing mean?, from 9 years ago, but I don't think it fully answers my question.
(Added on 8/15): After mulling over the comments below and seeing that my question has just been reopened, let me try a second iteration. (I trust somebody will let me know if this ought to be posted as a fresh question.)
Why is the grammatical category of "voice," which I have referred to above as (1), so named?
My understanding is that generally speaking, "voice" has to do with the relationship of participants to the action contained in a sentence. Possible forms of voice extend beyond active and passive, for languages have developed many ways for expressing different ways ways of acting/being acted upon. This is even true in English: "the book sold well" is technically passive but it imputes some agency to the book itself - unlike, say, "the book was sold by Amazon."
OK, BUT: how/why did the ancient grammarians who were in the business of inscribing speech as writing even come to denote this category as voice ? I just don't see that acting/acting upon has any intrinsic/logical relationship with vocalization, certainly not pre-Christianity.
It would be great if somebody could explain the linkage - or perhaps the "dead metaphor." Which brings me to an ancillary question: would it be correct to conclude that the grammatical idea of voice is (or was) in fact a metaphor, qualitatively no different than the various metaphorical uses of "voice" in writing- see (2)- above- which Lawler so helpfully describes in his 2012 post?