I've actually never encountered anyone with
Harper as a ln. As a fn, it's (a) a ln, (b) an occupation name and (c) indelibly associated with TKAMB. Which is a good book and all that, but not to my taste as a naming resource. I'd prefer to leave
Harper as a synonym for 'harpist', also because of the nagging, whining thought of someone constantly harping on something.