Not much market - I can do that, and play all the guitar parts as well (but I've been at it for 25 years). Might be some market in explaining what some of the more obscure lyrics mean to non-Americans! Seriously, though, I and others have found that performing certain of the songs seems to bring catastrophe and disaster on the household - be warned! I refuse to perform "Hellhound" and "terraplane", and there is a particular augmented chord in the A blues (eg, Dead Shrimp, Little Queen of Spades, Phonograph, 38-32-20) that I always play a little bit "wrong". The most distinctive feature of Robert Johnson's accompaniments is heavy use of the "tritone", an augmented interval which was known from medieval times as the Devil's chord and was forbidden in church music. I don't want to put you off - but there are some things we just don't understand.