Watch the Robert Nighthawk Style: Standard online guitar lesson by Andy Aledort from Slide Guitar Power
The Robert Nighthawk vibrato, very slow and very wide, and overflowing with emotion, is my absolute favorite slide vibrato ever. Playing in standard tuning, Robert could easily move back and forth from fretting conventional rhythm guitar chordal patterns to adding slide melodies between his vocal parts. The example here emulates his solo, played entirely with the slide. Robert possessed a very specific melodic sense in his solos, which I try to ressurect in the solo played here. Essentially, it is very vocal-like, and sounds as close to a guitar singing as one can get. Be sure to firmly anchor the fret-hand thumb behind the neck in order to replicate Robert's signature, emotive, singing vibrato.