The back D on my chanter only plays in tune when I play it off the knee. I’ve tried taping, and filling the hole a bit with Blu-tac, which will get it close to perfect, but its overly pressure sensitive then. There’s also a little unstableness with C#.
Help? Its hard to go from off the knee back D to second octave notes!
Have you tried fingering back D venting the C hole? If not, give it a try.
No E
Have you tried easing off a hair on bag pressure with back D and C#? Try easing off just a hair and then right back to jump to the 2nd octave.
The vented C hole works well with one of the reeds in my other chanter…I think that was quite common in the older days…O’Farrell’s tutor shows that as a back D option.
I tried the c vent thing- actually seems to raise the pitch more (its sharp to begin with, I should mention, almost an Eb). If I raise the top 3 fingers with the back D, its pretty much there, but thats really inconvienent. Any other ideas?
If you sit the reed further out in the chanter (add some thread to the bottom of the staple unless it’s the kind with the brass tubing slide), that’ll flatten back D more than the other notes. Sometimes it really works well and solves the problem (or at least gets it close enough that it can be brought into tune with a bit of taping), other times not so much.
Opening the reed slightly will help with the C# and back D unstableness, but with the weather getting cooler and drier, they may not really be perfect until April or May. I know my main reed is feeling the change, and soon will be a major pain to deal with until spring.
I’ve messed with taping, reed position (further in and out), and pressure, and I can get a decent (if not held out too long) back D, but its still not adequite. I dare not mess with the reed too much at this stage of the game, as I have only one reed. I think I might need to have a reed made for the chanter that’ll be more at home in the dryer weather (living in Wisconsin on the shores of Lake Michigan causes a huge range in humidity and temperature!) I don’t know much about rushes- and I think that might mess with the other notes too much (all the other notes are within a few cents of spot on compared to a strobe tuner)
If only there was a reedmaker who frequented this forum…hmmm… 
Time to start reedmaking maybe? 
I guess I’ll have to start skipping some lectures and give it a shot. 
Suprisingly, they don’t teach reedmaking here at UWM 