There’s a lot of articles out there on keeping your writing voice, and there’s a good few on staying true to your writing voice.
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There’s not much mention of something I’ve noticed though: how sometimes your writing voice can waver when you’re reading books by other writers. Sometimes you can even start sounding like someone else in your own work, because of what you’re reading.
That’s not to say that you should never read while you’re working on something. Then you’d never read anything.
I’ve also been thinking about how writing advice is mostly bullshit, so I’m not here to advise you. I don’t believe that I am in any position to go dictating to people what they should be doing and how: I’m just here to tell you how I’ve dealt with things, and to share my experiences.
So basically, to be honest, the way I keep my writing voice is to look at books by other writers as places of learning.
I keep the lines between my voice and theirs rigid in my head by focusing on what wisdom I can glean from their work, rather than being so completely absorbed in it that it starts cannibalising my own.
Read everything — trash, classics, good and bad, and see how they do it. Just like a carpenter who works as an apprentice and studies the master. Read! You’ll absorb it. Then write. If it is good, you’ll find out.
— (William Faulkner, interviewed by Lavon Rascoe for The Western Review, Summer 1951)