This piece introduces a new chord which is quite rare for
slide.
The tune is Motherless Children - based on the Eric Clapton version - interestingly
the earliest version I have of this tune by the great Blind Willie Johnson uses
no chord changes at all!
This is common to a lot of early blues where the slide doubles the vocal melody
and the chord changes are implied in the melody but not actually played.
The new chord is found in bar 12 played at the eighth fret - it's a Bb in D
tuning - note that this is a 16 bar sequence
The Tab