Uh, It's confirmed by Bayohne that it is a bow that "transforms". He said so in response to the speculation about the harp, which seems to confirm that it indeed "transforms" into a harp.

http://forum.square-enix.com/ffxiv/t...l=1#post349656

I don't really see where there's room for speculation, it was pretty much confirmed by a community rep.

Edit: Note, this is in response to the OP, I haven't read the entire thread, so not sure if anybody else brought this post up.