Hi Mike, thanks for your amazing teaching on GT. I am stuck. I am not understanding the drop D tuning 1/2 step for this Nirvana song. (how to tune the guitar down 1/2 step to the 'flat' notes as given in the TAB. When I click on the GT guitar tuner & I am not seeing a 1/2 step down tuning in the list. What is the best way to get this tuning correct? Thanks, Rick