The late John Fahey's website describes the music as "american primitive guitar." The piece Sharks may be a particularly good example of the primitive, yet innovative sound Fahey could achieve. Songza coughs up a minute clip of it:
Derek Taylor reviews Sharks:
A collaboration with Jim O’Rourke, taped in the younger guitarist’s bedroom, the album makes extensive use of echo, loops and samples on pieces like the bottleneck-by-way-of-sine-drone “Sharks” to create music that is equal parts ambient and terrestrial, fever dream and reverie.
I've been more strenuously listening to the music of Fahey for the last year or so. I'll say the same thing I would say about Miles Davis -- he was an artist, not just an instrumentalist.