I know this has been posted, but the search function has limited ability to find it for me… (In other words I looked, and can’t find anything)
For a flat set of pipes pitched in B: is this the true B natural (a semitone down from C, or a tone and a half down from D), or a Bb (1 tone down from C, 2 from D)?
Depends on the maker… some sets are sharp of A=440 standards
For a flat set of pipes pitched in B, it’s the B natural or first piano key below C. anything barely above or below just needs tuning. There’s lots of ways to retune a chanter or reed. Bb pipes are two tones, or four semitones below D.
Depends on where you’re coming from with the question. If you are asking about really old sets of pipes tuned to old tuning standards, it would depend on how old the pipes are, e.g. what once was C may now be B by today’s standards. If you are strictly talking new sets, I believe all makers are pitching their sets to the A=440Hz standard, so a B is a B, unless its a half a bee. Then it would be Eric. For more details see: http://www.wilken.freeserve.co.uk/Montypython/Songs/song14.htm
djm
Just to reinforce djm’s point, the old sets were often identified by their size. Clancy played an 18" Coyne, Williams Andrews is described as playing a 15 1/2" Coyne and so on. Modern makers I would expect to try to pitch their chanters somewhere is relation to concert pitch. My own B is actually about 17 3/4" although modelled on a 17 1/2" chanter to get it into “modern” pitch.
Play on your own or with a fiddler and you can be in any tuning, play with a flute or fixed pitch instrument like a box or concertina and you need to be in the current expectation of true pitch, whatever key your chanter is nominally.
Ken
DJM wrote:
so a B is a B, unless its a half a bee. Then it would be Eric. For more details see: > http://www.wilken.freeserve.co.uk/Montypython/Songs/song14.htm >
You have a warped mind. I like that in a person. 
Rick
But do you have a license for your pet bee Eric?
Fortunately, you don’t need a license for a cat.
djm
One: “That’s not a fish licence, it’s a dog licence with the word ‘dog’ crossed off and the word ‘fish’ written above it in crayon!”
The Other: “The man said it was a special licence.”
Mark (Minty Pithin rules ok!)