A Crazy Mess

Nope, no joke.  In fact, Pat Metheney plays one regularly.  He probably has a small army of people to keep it tuned, though. 

In fact, after googling up the video of him playing one, I think that one is his.

http://www.youtube.com/watch?v=Wp1wHZfZz9s

very interesting. from what i could make out, it is tuned as a harp/sitar. all the notes he played (apart from the bass notes on the heavy strung classic guitar) were open notes as per harp. he then added a little strum for effect as you would a sitar, but i think the main carrier of the melody (what there was of it) was played by the pianist.

dont get me wrong i'm not knocking this guy, he's very skillful and melodic in his own right. do you think he would want to join the other strings forum?

Pat Metheney is an internationally known virtuoso and one of the best guitar players on the planet, so I doubt if he's got time to come and educate us, although a boy can dream. 

I think there was more going on there than just that, too, Phill, for a couple of reasons.  An instrument like that is going to have sympathetic harmonies ringing out all over the place.  If you note, he never stops fretting on the guitar necks, even when he's strumming or picking on one of harps.  A harp is also not going to be tuned like a guitar. Harps (and this is a harp guitar) don't get fretted at all.  They're plucked or strummed, just like Matheny does in the video.   It is by necessity tuned to something open, or even a full chromatic scale if there are enough strings for it.