I have no worries - just curious!
I don't think DD (just turned 3) has an unusually good memory. I know several children who recite whole books, which DD has never done - she will occasionally pretend to read one, but will paraphrase rather than recite.
But she often spontaneously starts singing songs - I counted 5 which she was word perfect on (some quite complicated) and at least another 10 which she had a good bash at (independently, not joining in singing with someone).
Do they all do that?! I find myself constantly amazed! Not that I think DD is unusual, but development at this age is just awe-inspiring 