The current pipes|drums Poll asks about which note is most difficult to tune. (By the way, the poll system we use is limited to six choices, hence omitting specifically low-A, B, C and high-A, which I think are not that hard for most bands to get right.)
So far D leads the race, with F coming from behind (oo-er!). My choice is D, evidenced by the fact that it is by far the note that is most likely to blare when listening to a band. My second choice would be F, and actually bad F’s are harder on the ears than bad D’s.
I wrote about “The Brown Note” a while back (two years already?!), suggesting that instead of judges having to write again and again “D’s not well blown,” they could just write, “Brown Note,” and bands would know exactly what was meant.
In reality, more often than not a pipe section’s D is well tuned; it’s just not well blown. It’s a note that is prone to relaxation. Pipers love to take a little break with big D’s, all that air rushing through open bottom-hand. All pipers really have to do is be sure to time their blowing so that they’re blowing steadily, not breathing/squeezing, through the longer D’s, and, voila! D’s no longer sag, and the dreaded D becomes the mellifluously positive note that it deserves to be.
Well, that’s my theory, anyway. Your brown note may vary.