You have to tune it in drop C in order to get that low C, but you can play it in tuning too if you play everything two frets lower and leave off the power chord. You also don't to play the octave, either note by itself will sound alright, but that way sounds the best. d|-----------------------------------| A|----10-11-10---11-10---11-10--8----| F|-----------------------------------| C|0---7--8--7----8--7----8--7---5----| G|0----------------------------------| C|0----------------------------------| d|----------------------------------| A|----10-11-13---11-10---10-11--3---| F|----------------------------------| C|0---7--8--10---8--7----7--8---0---| G|0---------------------------------| C|0---------------------------------|