Vocal Skill Level
Your vocal skill level also influences how unique your voice may be, because if you learn how to create new sounds, those are then new options for you. A lot of singers rely on instinct alone to decide their sound for them, but if you know how your voice makes varying types of sounds, then you know how to do a cover of a song and sound nothing like the original, making your singing more…original.
I have worked with young singers who have fantastic vocal habits and will sing a song close to how their favorite artist sings it, but if you ask them to “make it their own” they wouldn’t know how to go about that. If you take these same singers and ask them to sing a song without a pre-defined genre, like say, “Mary Had a Little Lamb” they often don’t carry into their singing all the runs and varying tone qualities they had carried over from their favorite artists.
Why is that? They sound great, but skills still need to be built to know what they can do with their voice and then decide what sounds to make as an artist. So in this way, you can sound great, even though you haven’t necessarily built the skills to sound unique, or bring your great sounds to a song that you have no sung examples of.
On the other end of the spectrum, you have singers that want to sound like a particular artist, but they haven’t really built the tools and skills necessary to sing like the singer they’re hoping to emulate, and in the process run into a new sound. I also see this quite a lot in singers, and sometimes this works really well, sometimes not, a lot of this depends on whether the singer is doing these new resulting sounds in a healthy way.
With the vocal skills and know how, it IS possible to have your own unique sound by design.