a blues harp.
“Effect pedal wizard and Chicago studio musician Bill Ruppert” makes his regular guitar sound like a blues harmonica with four Electro-Harmonix pedals (HOG, Micro Synthesizer, Wiggler, Holiest Grail).
He does a pretty damn good job of sounding like the real thing. Though admittedly you’d have to spend a bit of cash on those 4 units, going by Google shopping prices knocking on for 800 quid, so it might be cheaper to just find a real harp blower, or learn yourself.
He also gets the synth sound Pete Townshend used on the Who’s “Won’t Get Fooled Again” with a Hog and a Stereo Memory Man with Hazarai…