I get this strange sound on my 1st string when I play it open, the 12th fret, and a few other frets along that string. I only have this problem with that string. If you were to detune your 1st string and play the 1st and 2nd strings open together, you get that kinda tremelo/vibrato sound. Thats what it sounds like when I hold a single note on some spots on the high e. Anyone got any info about this?