The significance is that both Willie McTell and Leadbelly both tuned standard tuning pitched approximately at B. That is, if they played what looks like an E chord, it would sound like a B chord, pitchwise.
Bear in mind that they were using 12 string guitars that had a scale length approximately one to one and a half inches longer, at 26.5 inches, than the 6 string guitars being made at the time (and today). The old instruments were really thought of as having a baritone voice, to the guitar's tenor. But, when 12 strings had a resurgence in the '60s, makers built them with scale lengths similar to 6 string guitars, giving them essentially ther same voice. Until, of course, Todd and others decided there was enough market to make ladder braced 12s with the original scale length.
There were those who played 12s, back in the day, who pitched them the same as 6 strings. Barbecue Bob is probably the most well known, and George Carter did as well. Not sure where John Byrd and others tuned.
As to "shoulds" I don't really believe in them. On my 1920 Oscar Schmidt Soveriegn I use the sets that Harry Lewman gets from La Bella, which are a touch heavier than those Todd has, and I find that the tension when tuned to B is just right for my playing and moves the top well. Taking a modern short scale 12 down to B might give some pretty sloppy strings and not a whole lot of tone, even with pretty heavy strings. So I guess many settle for D. I would say find what works best for you by trying different string gauges and different pitches for the songs you play. There are no rules except for getting good tone from your guitar.
There is no way I could sing McTell's Brokedown Engine even pitched at D without rewriting the melody for the last phrase. Of course, I could rearrange it into, say the key of A, and then capo up 2 frets to B, but that's for someone else. To each his own. I like how Willie played it.
All for now.
John C.
