Jerry,

You want "get offa my note"? You ain't lived til you try being in a bluegrass group (maybe you've done it). Those guys-- at least some-- are downright fanatical. Not only does the note have to be in the chord--that's fine. But only a particular voice is allowed to sing a particular note. Even if 2 singers want to switch notes-- (no duplication)-- that's frowned on too.

I love close harmony--and I love bluegrass. I'm very willing to go to a 5th if somebody else wants the 3rd. But the bluegrass approach (it seems to me) is just too rigid--though I agree with those who frown on "uptown" chords in bluegrass.

What I do in bluegrass these days is just to sing the bass--1 -4- 5- 1-- (or variations on that)-- usually. But in bluegrass there's only room for a bass in gospel bluegrass--well, I suppose bluegrass is the "high and lonesome sound"--so that's the way it is.

Sea chanteys--well I had a sea chantey group once upon a time. We only rehearsed once a year--for our one gig. It was pulling teeth to get all the schedules to coincide--though there were only usually about 7 of us--for even one rehearsal. So one year we had none--and it went just fine. Rough edges in sea chanteys--no problem.

When we did rehearse --well it depends on what your goal is. If your goal is richness of sound, or close harmony, you don't want much duplication. If it's power, or a stark beauty, duplication adds. So in chanteys, it's often a good idea. Classical composers often used duplication --esp on 1 and 5--tonic and dominant--to convey power--figuratively and literally. And in Sacred Harp (which I also sing). there's lots of duplication in octaves--it does add to the power of the sound--especially if in different voices--say bass and treble--and especially if there's no 3rd.