[kermitology]

Typically Dropped D tuning is just dropping the low E by a whole step.

But that song is tuned to C..

So instead of EADGBE it's CGCFAD. Usually a guitar tuner will allow you to tune to Eb or D. My old tuner could do that, and my foot controller has a tuner in it, so it tells me the note that my string is tuned to.