I didn't get Dave's term "shirt", but i transposed it in my mind as "position". So i started looking at the fingerboard, and plugging in notes, and found the 1/2 step movement on the 2nd string for the 4th in relation to a note fretted on the 3rd string. Dave mentioned this last year when i took his guitar class, and i didn't quite understand why the 2nd string was different. I just kinda blew it off and said "whatever, teach me some chords"---- Now i see the reasoning behind the difference...The 2nd string on the guitar is tuned to a note that stays natural---no flats or sharps. Now,why did the designer of the guitar tune it in 4ths? This would be an interesting study. There is a reference to a person in the Old Testament of the Bible (the Book of Genesis)given credit for the invention of stringed instruments. I'll find out who that is, and we can expound. Several of the Psalms are written to be played with stringed instruments, but i'm not sure the guitar goes that far back. They may be referring to the harp or lyre...but i think a lyre has frets....