(this lesson requiers an electric)to do this use a pentatonic to go down to the 15th fret of the first string. then slide to the 17th fret with a little vibrato for style. then hammer on to the 20th fret of the second string with your third finger while your first finger is still on the 17th fret of the first string. bend the second string all the way up slowly untill it matches the sound of the first string. then bring it back down slowly letting every half step be heard. this makes the guitar growl like a cat with a very deep voice. make sure that your third finger does not mute the first string, to do this keep it well bent above the fretboard.
this is a scale sequence you can use to get to the 17th fret.