Those drop tuner keys
1I looked it up and the banjo tuners I was thinking of are called Scruggs or Keith tuners, and you can set a second interval with them kind of like a pedal steel. They cover it on here at around 6:10 if the YouTube link doesn t automatically direct you there. The sound is a little synthesized with all of his pedals but the way he is able to switch tubings is pretty amazing.I think Clarence White had a couple on his famous telecaster.
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