I love the sound of these steel resonator guitars. Here are Taj Mahal playing a tricone, and Keb' Mo' on a single cone, from the 2013 Crossroads performance. Diving Duck Blues:
Great tune, and Jerry Douglas has been one of my favorites since he was a pimply teenager (think back to JD Crowe and the New South, first incarnation, with Ricky Skaggs and Tony Rice as well). For historical context, John Dopyera designed all three models of the original resophonic guitars, the tricone and single cone while he was still part of National Steel, and the Dobro when he and his brothers left to create the Dobro guitar company. The Dobro has an inverted resonator cone inside, which projected the sound a bit better and richer.