Stewie, As far as I can tell there is, as you say, only one recording by Lead Belly of "Line 'Em"; this was with the Golden Gate Quartet in 1940 but has been issued by RCA and by Document. There were no Library of Congress recordings. So your idea may well be correct; did he learn it from the Lomaxes rather than the other way round. Later recordings of this were post 1940 for Asch. Dr John