This tune is very loosely based on Blind Willie Johnson's " How Dark the Night How Cold the Ground " which has the distinction of being one of 27 samples of music included on the Voyager Golden Record, launched into space in 1977 to represent the diversity of life on Earth.
In the tune Blind Willie sings or hums ( there is no lyric ) along with the slide melody while keeping a drone chord sound going in the background - there are no chord changes - in this version the drone is an open E ( on the original it's closer to D ).
I have spared you my vocalisations but the idea is to sing or hum along with with the tune once you have it worked out.
The slide parts of the melody are all on the top string but there are some fingered melody notes on the second string.
For reasons of clarity I have just tabbed out the melody line.
The last 2 bars of the tab give an indication of the sort of thing I'm doing on the open E chord to keep the drone going — basically just arpeggios using thumb for the bottom string and index finger for the other notes.
Although there are no chord changes as such, there is an implied change towards the end - this is achieved by dropping the drone for this bit, I also hit the 5th string open once at this point so the implied change is to a B chord.