I had to do a lot of driving this month, and I took the opportunity to listen to some audiobooks while doing so. One of them was a book set in England, by an English author, but for some reason they cast an American voice actor. While this was a bit jarring in some ways, it could have been alright as long as the actor remained consistent in how he did things. Unfortunately, he only decided a little over halfway through that some of the characters—including ones he'd already established voices for—would now have English accents. Not only that, but he fluctuated in how one character's name was pronounced, making it unclear if there was suddenly some new character being referenced. So let's talk about the importance of consistency, and how both the talent and the client can help establish and maintain it.
We've previously discussed what direction notes are and how important they can be. But to reiterate here: they are a tool for the client to let the talent know specific things, such as pronunciation, tone, pacing, etc. While audiobooks have the story itself to serve this function, other things such as training courses, documentaries, explainer videos, etc, may need to employ direction notes to convey this information. This can help the talent remain consistent in how they say things like dates (two-thousand and twenty vs. twenty-twenty), names (is Naomi Nay-oh-mee or Nah-oh-mee in this script?), and other important elements. It also will let them know if you want any accents or to otherwise alter their delivery in some way.
If you're the talent and you're dealing with any kind of narration, regardless of whether or not it provides direction notes, it is up to you to take a moment to analyze things to ensure you keep things consistent on your end. Maybe no notes are provided at all, so you have to make the choice yourself as to how you will be pronouncing that name throughout the rest of the script (after ensuring you're at least using an accurate/acceptable pronunciation in the first place), or how you'll be saying years or other numbers. For something like an audiobook, it's always a good practice to determine a specific voice for each character before you start recording, and keep notes on that. If a character is meant to be of a certain nationality and their accent is expected to reflect that, it's important to include that in your notes so you can remain consistent with it as you go.
But this also works for other forms of narration, and the kind of voice you're using throughout it. It would be weird to start out something sounding perky and young, and randomly shift partway through to a more calm and mature voice. Even if the direction notes want you to switch things up and take on a more serious tone in one part, try to do so while using the same persona you've used throughout the rest of it. So in that example of starting off young and perky, keep the youthful quality even while switching to a more serious tone.
Sometimes if a project is long, the you may need to take a break while recording. When you start back again, make sure you listen to earlier parts so that you can match that same vocal delivery. If you need to, practice a few lines, or repeat back something form the recording a few times in an attempt to exactly match it. This will help the new recordings to more seamlessly flow with the earlier ones.
Consistency can be hard to maintain, especially for longer projects, but it's part of the job. It takes just a little effort and awareness, but it makes a world of difference.