I'm not sure if being to perform certain accents and dialects almost perfectly is echolalia, since I do that often. I can perform accents, but they aren't accurate.
I might have been experiencing echolaliac patterns in my mind, as I can get stuck on this phrase in my head, and, even though I don't say it out loud, it keeps repeating.
I can sometimes actually mimic voices of a different gender. For example, I can make my voice sound extremely deep and masculine (I'm female, by the way), and it just sounds male. I can mimic certain character's voices, which my sister likes to hear (especially if it's a hot male anime guy).