Drop D tuning,  Capo on the 3rd Fret

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-------------------13---------------------------------------------------
--13/-------------------13---------------10-------------------10--------
--------15---15-------------15------13--------13---3----13--------13----
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                  [Let Ring---]    [---Let Ring---------------------]


Not sure if this looks right...it is the exact tab but this text editor sux.
  Took me a while to figure out what they were doing.  After seeing them live
it was a piece of cake.  After you play the riff, the pedal tones are just 
6th string open (F) and 4th string open (F).

The reason for the drop D tuning and the capo 3rd fret is to maintain the 
F chord droning.  If you watch any of the live vids on youtube you will
see the capo 3rd fret. 

Have fun.