Depends on what you call "natural range''. If you can do falsetto--( I know you know what that is, though it's Italian)---and make the transition from full voice to falsetto smoothly--without being obvious, you can extend your range substantially. I have a lousy range--but falsetto just about doubles it--to about 3 octaves.

I owe my falsetto--and therefore being in any chorus at all--to the Beach Boys--and years of singing in the car with them. (Don't ever try Frankie Vallee--that's a mistake.)

The smooth transition is the crucial part.

As has been pointed out, there are lots of songs with substantial ranges--if that's how you would like to stretch your range---including Fathom the Bowl, Northwest Passage, and Danny Boy--among MANY others.