This is part of the intro to the version he plays on "His Greatest Hits Vol II". I think 
is one of the best versions he plays. Anyway I really like it and I hope someone will 
the tab. This is just what i've figured out, I hope its correct. : )

Wont get too technical on the bends and such, this is mostly bare bones... mostly.

... I think it's in Standard down a 1/2, i could be wrong but it sounds ok to me.

Legend
  b= bend
  h= hammer on
  v= vibrato
  ~= hold note
  /= slide, slide to note
( )= harmonic, ... ?
 pb= pre-bend
  r= release bend

With Wah, slight vibrato on each note, more on indicated notes
eb-----------------------------------------------------------|
Bb-----------------------------------------------------------|
Gb-----------------------------------------------------------|   X2
Db-12h14--14--12vvvv-----------------------------------------|
Ab-12h14---------------14--10-----10vv-----12h14--12vvvv-----|
Eb-----------------------------0--------0--------------------|

Theres a small bit I missed in the transition played at the end of riff 1 sounds like,

Ab--10----------------|
Eb------12vv\\\\(0)---|
Muted a bit i think.


Slight Vibrato on each note (riff 2)
eb-----------------------------------------------------------|
Bb-----------------------------------------------------------|
Gb-----------------------------------------------------------|
Db---------------12------------------------------------------|  X2
Ab--------12/14------12~~~--10-------------------------------|
Eb--0~~~~------------------------12vv\\\(0)------------------|


eb-----------------------------------------------------------|
Bb-----------------------------------------------------------|
Gb-----------------------------------------------------------|
Db---------------12------------------------------------------|  X2
Ab--------12/14------12~~~//14-10----------------------------|
Eb--0~~~~-------------------------12vv\\\(0)-----------------|


eb-----------------------------------------------------------|
Bb--15b-15b-15b--12--15--15b-15\\\\\-------------------------|
Gb-----------------------------------------------------------|
Db-----------------------------------------------------------|
Ab-----------------------------------------------------------|
Eb-----------------------------------------------------------|
                v---v dont release just play bent
eb-----------------------------------------------------------|
Bb--15b-15b-15b-pb15--12~~~~~~\\\\\--------------------------|
Gb-----------------------------------------------------------|
Db-----------------------------------------------------------|
Ab-----------------------------------------------------------|
Eb-----------------------------------------------------------|


Thats pretty much what i've got so far and with my talent all I can figure out for now. 
riff 2 during his singing (the only one numbered), freestyle it for fun idk, have fun 
it. Blues is all about feeling right?


Email me hottharvey@hotmail.com if you have more please, i love this song.