Without any deeper penetration of this I´d say he´s using a G harp in 3d pos, and a D in 2nd. And the D harp ain´t necessary for the melody, just some riffing, thus making the impracticality of holding two harps at once a bit extra-curricular. But it looks great. (Also, this is most certainly not a live recording, so he could have been switching harps all the time if he´d wanted.) Great sound.