I'm getting ready to go to Portland to do a two-day workshop (eek-- they are going to be so bored with me before it's over), and one element I want to address is voice. Well, nothing like choosing an amorphous concept. But I had lunch with a friend who is getting her PhD in Rhet-comp today, and she said the research now suggests that writers don't have a single "authentic" voice, but rather that writers assume a different "persona" for different rhetorical situations. Of course, we all know that we're going to "sound" different when we're writing a technical manual and when we're writing a thriller. But I think even different novels present different rhetorical situations, and a single voice, however authentic, might not be effective.
(BTW, some of the research has to do with something I've come across working in a university writing center-- following a new graduate student whose initial writing "isn't graduate enough". I occasionally tutor grad students who have been told by a prof: "You don't write like a graduate student." That is meant, btw, as a criticism, not a compliment. The voice in graduate papers is more neutral, more analytical, not "This is an amazing book," but "This comprehensive history offers insights into...." There's an expectation of a voice-- one of those "you know it when you read it," but not necessarily anything I can identify point by point.)
So... think about your own writing. Do you think you change voice when you change books? Or do you think you "write to your voice"-- maybe not trying the type of book your existing voice wouldn't fit? (For example, there's nothing so excruciating as a dramatic writer who is forced by an editor to write comedy... either you're funny or you're not, let's face it.)
Well, maybe I should ask: Do you think you can create a comic voice if you aren't (previously) funny? (I just asked my husband, and he said, "Sure," and when I demanded and example, he replied, "You." Not funny, babe.)