I have two guitars which I occasionally decide to play. A Fender 12 string with a horrible rattle when I play the 1st string open and a Harmony 6 string which has a 6th string which sounds sound like a badly synthesised sitar when I play IT open. Capoing at the first fret prevents this happening but It isn't a solution. I have tried changing the strings and being shamefully ignorant in these matters am appealing to the 'Cat for help.Thank you in anticipation...the fB