Gah! I missed this earlier: Ariel appears as a harpy in the play, so "Harper" probably alludes more to that than the harp in Tempest art.

I love a Tempest
Because I love "The Tempest," I want to point out anything that could be even vaguely related to the play and this episode:

argh
I wish more people would just read Alan Moore's original stuff instead of getting introduced to it through butchered movie adaptations.