Only if the avatar is capable of speech. Like if someone's avatar is some inanimate object, I'll just read it in my voice. Other than that I'll make one up.
I used to imagine MadaraXIII's with a raspy voice, but then I heard his actual voice, so I use that one now.
I used to imagine MadaraXIII's with a raspy voice, but then I heard his actual voice, so I use that one now.