I took singing lessons back in the 90s. My actual voice is quite low but I have the ability to raise the pitch just enough to sound more fem. But as others have said, nearly all of the CDs I've met don't even try to change their voices.
That said, if you really want to pass as a female 24/7 it's worthwhile to pursue IMO. For some trans I've met, a fem voice seems to have come naturally.
