Dave Van Ronk was one of the iconic pioneers of Ragtime Guitar, and carried on in the styles of Reverend Gary Davis and Blind Blake, and and brought the sound and techniques down to the next generations. His 1985 album, Going Back To Brooklyn featured just Dave's guitar and vocals performing original compositions, most of which had been recorded years before with other musicians. Gaslight Rag is Dave's homage to The Gaslight Cafe, one of the main folk music clubs in Greenwich Village in the 1960s.
This lesson just looks at the instrumental accompaniment the Dave plays while he sings three verses. It is really just two sections with a short intro, the third verse is really just a slight variation on the first one.
The sections are fairly standard ragtime progressions, with one section in C Major and the second in F Major. Dave usually plays his F chords by wrapping his left thumb over to play the sixth string, and this is recommended for this tune, but not completely necessary.