Watch the Slide Vibrato online guitar lesson by TrueFire from Play Blues Guitar 7: Slide Approaches
Slide Vibrato - Overview is a video guitar lesson presented by Andy Aledort and is sourced from Slide Guitar Power.
Along with using glissandos, sliding up or down to a specific note, the technique that most evokes a vocalesque quality on slide guitar is vibrato. Repeatedly moving the slide back and forth (higher and lower) along the length of the string creates the sound of a slide vibrato. The width of this movement, as well as the speed, this is every player's choice; just keep the center of the vibrato movement over the fret for proper intonation.