Sidney Robertson Cowell recorded Warde Ford on several occasions during 1938 and 1939, in
Boomtown (Central Valley), Shasta County, California. Copies can be heard at the Library of Congress site  California Gold:

Warde Forde: recordings

I don't have that part of Bronson, but the online recording is clear enough. The missing pieces are:

What ho, what ho

And like thunder their cannon did roar

Mr Ford distinctly sings "robbing" rather than "robbin".