this is going to seem VERY vague, but i hear it in some van halen song before (i think van haken) and eddie kind runs his finger along the muted low E string from maybe 7th fret to 3rd fret.

it has been bugging me for soooo long, anyone have a clue
He just plays a series of natural harmonics. They're all along the string - not just at the 12th and 7th fret. They're a lot closer together further down the neck.

He doesn't mute the string, he just lays his finger lightly on it while picking, not fretting any notes.