hey im trying to play the symphony of destruction solo and when i play it after the 12p10 i strike the 12th fret on the b string but it keeps ringing is it my guitar?amp? or my playing?

Also on hangar 18 when playing the intro how to i fret the strings without getting dull sounds.
It seems like your hitting a harmonic on the 12th fret.
Gibson Faded Flying V

Marshall MG100HDFX
Marshall MA50C

Boss DS-1
Digitech RP50
Digitech Whammy IV
Vox V847 Wah Pedal