Voice is more than just style. It’s not that hard to imitate a style, as anyone who has read my Raymond Chandler–J. R. R. Tolkien crossover will have seen. Even the really out-there stylists can be imitated–you could, for example, mix a World War II engineering text with random pages of Fear and Loathing in Las Vegas to come up with a fairly good imitation of Pynchon’s Gravity’s Rainbow. You would not, however, have Pynchon’s voice, the thing that can make a forty page digression on an obscure meteorological phenomenon in Central Asia seem gripping, goofy, and lord help us even a bit profound. (If you like that sort of thing; I do, or at least I know I did once.)
Voice is a lot of things: but if I had to define it for myself, it means using all your quirks, knowledge, style, tics, vocabulary, word choice, hell, even your spell check and thesaurus, to create an effect that not only communicates what you want to say, but does it in a way that is uniquely you. Maybe once we’d have called it wit, but this is America and the twenty-first century, and we don’t have time for anything that can’t be barked out at a personal improvement seminar.
Voice is a strange, ineffable thing, precisely because it is where honesty and rhetoric, self-confidence and self-presentation meet. Voice is the ability to be completely yourself in your writing but in a way that draws people into your unique world. A shift in one direction is pandering, a shift in the other is solipsistic, and voice is always, always contingent on where you are as a writer at any given point and who exactly you are writing for. As Minou points out, this balancing act is doubly difficult when you are a member of a marginalized group, when efforts at honesty and authenticity are met with incomprehension.
Go read it.