It was while rewriting a scene that I accidentally stumbled upon a great tool for checking character voice: dialogue.
That might seem obvious since dialogue is literally a character using its voice to speak, but let me tell you how you can use it as a quick voice "test."
In earlier drafts, I had written a character named Aunt Minnie who was the best friend of my MC's late grandmother. Minnie was an eighty-year-old sweet grandmotherly-type, with a playful attitude and a flair for making inappropriate comments. I loved Aunt Minnie, but ultimately decided to rewrite her into my MC's actual grandmother, nicknamed Gams.
Gams is also an eighty-year-old grandmotherly type with a flair for making inappropriate comments. BUT she's also a former principle dancer at the New York Ballet Company, owned her own dance studio until she had to retire, and was my MCs original dance instructor.
I assumed that I could leave most of the scenes between Aunt Minnie and my MC the same even though the character was changing, with a few minor tweaks here and there. But when I started reading the dialogue I realized that it no longer fit.
It takes an immense amount of focus and discipline to get accepted into a revered ballet company, and to become a principle ballerina at that company takes even more discipline. When Aunt Minnie spoke she was funny, almost childlike in some ways, and her laissez faire voice no longer worked when I started to piece together the kind of woman Gams was: focused, determined, and perhaps even a little critical. In short, they were two distinct characters with different motivations who needed two distinct voices.
Here is a quick trick for checking to see if your character has a unique & distinct voice:
Imagine a new character that is like your original in almost every way, but give them a slightly different back story and/or hobby. For example, maybe this new character has a tiny chip on their shoulder because their parents are going through a divorce, where your current characters parents are happily married. Now go back and read some of this character's dialogue, but with the slightly modified character in mind. Would the existing dialogue work with the newly imagined character? If the answer is yes, you are likely suffering from a lack of voice, and you might want to take a step back and figure out how to infuse your character's uniqueness into the way they speak. If the answer is no, congratulations! You have written a character with a unique POV that is reflected in the way they think and speak. In other words, you've created a distinct and unique voice for that character.
Give it a try and let me know how it goes.