It sounds like theyre using a 12 string guitar or an effect. Drop C Tuning - C G C F A D Legend h - hammer-on p - pull-off D|----------------------------------6--------------| A|-----9h10-12--10-9h10p9------9h10---12--10--12---| F|11----------------------11-----------------------| C|-------------------------------------------------| G|-------------------------------------------------| C|-------------------------------------------------| D|--------------------------------------12-10-------------| A|-----9h10-12--10-9h10p9----------9h10-------------------| F|11----------------------11--9h11-----------------9h11--9| C|--------------------------------------------9h11--------| G|--------------------------------------------------------| C|--------------------------------------------------------|