Well, I wasn't really referring to the copying aspect as much as I was to the timed aspect. Besides having to play the notes in the right order, you have to play them at the right time. :/
For the harp, I feel like a free-style kind of ocarina would be better. Like, you have the keys wertyuio each correspond to a note in a scale, or as far as the fact that it's a harp goes, each would correspond to a different string. Then the player could pretty much put together any melody, as long as it's in the scale you choose.
I'd recommend NOT using a plan ol' major scale, though, that would be kinda boring, and not fit with the harp as well.