I never saw it, being born after the event like, but my dad used to play a 7 string in a 'gypsy band' when he was a lad in Poland. He generaly got arond playing different tunes on a standard 6 string, in later life, by re-tuning the sixth so I guess the extra string was physicaly above, musicaly below, the sixth.

He also mentions an 11 string! 7 string as above with 4 tuneable 'drones' - I would love to see the length of the finger barring that neck;-)

DtG