I finally tracked this down. I had the album this track was on – European Impressions – back in the 70s, and I loved what Coryell could do with an acoustic guitar. I managed to figure out bits of this piece, but not much. It’s a long suite with parts ranging from atonal solos to jazzy strumming. This is a video of him performing the piece live, sometime in the late 1970s or early 1980s. I saw him perform this solo acoustic stuff once, of all places at the Rasthaus in the Queens College student union (I think). It was an amazing concert. I’d love to get this album; it’s out of print, and I don’t have turntable, so if anyone has it, get in touch.
In any case, enjoy this 9+ minute example of true guitar artistry.