It's very similar to a 12-string guitar, where on the top few string sets (courses) one of the notes is tuned an octave higher.
He doesn't have a lot of recordings with this sound, but I really love it. I'm thinking that if I get a low tension classical guitar string or maybe
even a ukulele string I might be able to tune it up that high?
I've also heard some recordings of violinists doing this and it sounds really great.
You could take the high f course from an Iraqi string set and tune it down to e for the 3rd course on a Turkish oud. It wouldn't put too much pressure
on the soundboard either.