I’ve been playing Great Highland Bagpipes for a few years now, doing pretty well even if I say so myself. I do have one question: can anyone tell me why the chanter isn’t in tune with itself? I have a handfull of different chanters and all of them have to have the holes taped/ or undercut or whatever, in order to flatten or sharpen and bring in tune. Not that I’ve not asked this question of various persons in the past, but never really understood the answers which I received. One fellow said that it was because the chanters were produced at sea level and as you increase in altitude it affects the pitch. Really??? 
I play several different types of flutes and whistles and they are, if well made, in tune with themselves regardless of where they have been made or how high I get (not a reference to drugs). Actually, I have a second question–would anyone out there care to recommend a chanter that is in tune with itself, because I’m sure as hell tired of messing around with all of this tape? 
Try using bees wax.
It’s mostly the reeds not the chanter. There is no direct embouchure on a bagpipe reed therefor in order to make up for minor inconsistencies in tuning you have to use wax/tape or adjust the reed seat. It’s like asking why do drones have slides on them - why not just have a solid stick that’s always in tune. Once again, it’s the reed (and to some extent if the pipes is made of wood- that changes slightly too). Just be happy that you play an instrument with a critical mass of players large enough to support an industry of pre-fabricated mostly pre-tuned composite and cane reeds. I make reeds out of plastic Burger King cups. Reeds are like snowflakes, no two are alike. That’s the most poetic thing I’ve said all day.
NO - because irrelevant of the altitude, atmospheric density and atmospheric pressure are always proportional to each other, so this doesn’t matter. Temperature is a much greater factor, the higher sound velocity at higher temperature can bring the overall pitch noticeably up (or down at lower temperature) but it won’t affect the tuning of the chanter with itself.
As ciarameddaru said, if a chanter is not in tune with itself it is most likely a dismatch between chanter and reed. Today, the vast majority of GHB chanters are produced to the highest standards of precision. Same goes for the reeds, but not every chanter likes every reed, which doesn’t necessarily mean the chanter or reed is not a good one. Many people then adjust the chanter to the reed (if you now wonder why they drill, undercut and carve the toneholes of an instrument worth 200-300 $ to make it fit to a 10 $ reed - I don’t understand it myself. But many chanters have been spoiled this way). Almost every chanter I’ve seen so far that required tape had been altered beforehand. Some pipers (and Pipe Majors) have their own idea of tuning, therefore you find band chanters that have all been altered the same way. The GHB chanter tuning has undergone major changes in the past decades, the tuning has become much smoother than it was 60 or 70 years ago. In the 1970ies there was a fashion of tuning high A very flat (and often scratchy, which today would be regarded as a reed fault) so even the physical constant of the octave is not in every case constant. Many chanters have been altered in order to play along with instruments in equally tempered tuning, like keyboards or guitars. Of course, we are talking about natural materials which are subject to change - a wooden chanter will not be the same after two years of playing, a cane reed changes within a couple of hours of playing.
its the reed. staples vary, cut of the cane varies, even with superb QC. Plus, each reedmaker uses diferent dimensions.
thereforre each individual reed must be carefully tuned to its coresponding chanter. often over a lengthy period of time. My Strathmore reed is approx 6 years old. Strength of blowing affects intonation also.
MacLellan with straight cut Shepherds.
Gibson with Troy’s
Krons with Higgins
Atherton with Gilmour.
Have all worked well for me.
I have yet to find a good reed match for McCallums.
There will always be a need for some minor adjustmnt, on any bagpipe, but I have had luck with the above combinations using very little tape.
I cannot say that Beeswax is highly reccomended for the GHB. Other pipes, sure.
Humidity& temperature affect ghb reeds.
its also very true that chanters which have been carved are the most difficult to tune.
sorry to double post,
an important concept though-
the inside of your ghb chanter is a truncated cone. flat at the top. the interior cavity of the reed must supply the remaining space to bring this cone to a perfect tip, you follow? even a little off will alter the vibrating air column and position of its nodes.
with vents at precise points (nodes) in the air column, fingers open& close to obtain pitches of different frequencies.
hate to sound like a prick, but, if you want to lose tape etc, either you got to go through a metric buttload of ghb reeds to find just the right one for your chanter, get really really good at reed surgery, or get a electronic bagpipe. but I understand your fustration, believe me. good luck psychodonald.
The oval-holed (aka, “pre-carved”) McCallum band chanters go good with Ross reeds. I’m currently using a Soutar reed in my McC2 McCallum chanter and it sounds nice.
ZdF et al. Thank you much for your response(s). ZdF, that makes all kinds of sense and helps a great deal. Yep, it’s a frustration, no doubt, but well worth the effort.
Highland-piper I have a McCallum band chanter, newly purchased for the UPB. Based upon your suggestion, I spoke with a man at Hendersons today and inquired about the Soutar reed and he recommended the reed as you have done-- I ordered three. Ross reeds are apparently back ordered at present. Don.
I use a MacCallum chanter and typically a Ross, Shepherd or McGaritty reed. I’ve noticed that if I adjust the reed by moving it up or down will make it better or worse when in tune with itself. In fact, I have one goofy reed where it needs to be practically falling out of the chanter in order for it to be complete in tune. If I were to tighten it in its place and pitch it higher, the low A and high A become horribly out of tune. Go figure.
I’d experiment with the reeds mentioned above and definitely look at replacing your chanter with another maker. My pipes are made by Gibson, but I never like the sound of the chanter, and replaced with the MacCallum. It turned out that my old pipe band had converted to MacCallum’s collectively, which I think you’ll find with other bands too.
Good luck in fixing your sound issues! It’s a constant struggle!!
Matt
Well first off Im no Guru, but after 15yrs at it I think it reasonable to say I have a fair grasp. Tuning the chanter is the bottom line. I have recently come across a great short cut, a saul tuner. It allows fine tuning in a much shorter time . After a certain amount of time the ear gets fatigued and this tuner is well worth the money IMO, you can set it to be more accurate than the standard settings as well. I dont use it for my drones but for the fine tuning of the chanter its great. getting the high and low A right for me is the key.After that a little bit of tape is normally needed for the D. and possibly the high A to get the E a perfect 5th.Instead of undercutting though I have no problem doing so if necessary. For me I like my high A dead on so I can simply tune to this note and everything else falls into place.
Yes its expensive, but what price peace of mind and true harmony? its priceless! 
To address the last point first, flutes and whistles don’t have reeds. But it’s sure possible for one person to play out of tune on a flute that’s perfectly in tune for someone else.
Why tape is needed is because each reed has a specific unique scale built into it. Try ten reeds by the same maker, made in the same batch, in the same chanter and each will produce a slightly (or oftentimes more than slightly) different scale. Sometimes it’s only a couple cents one way or the other, but enough to require tape on the hole. Why? Sax players don’t need to move tape with each new reed! It’s because on the sax or clarinet your embouchure is a huge part of tone production, and very slight (and often unconsciously done) adjustments in the embouchure bring everything into tune.
But a piper is faced with three issues the sax man isn’t 1) there’s no embouchure on the pipes, so the chanter scale has to be precisely correct at one even pressure and 2) each note of the chanter scale is heard over a fixed drone so the tuning has to be exact to the cent and 3) the bagpipes are usually played nonvibrato meaning the tuning has to be much more precise than it would be on a woodwind played with heavy vibrato like the orchestral flute.
So the piper must use tape. Someone mentioned wax, but wax doesn’t work on modern GHB chanters because the walls are so thin that there’s no “chimney” for the wax to sit in.
New McCallum chanters have oval holes, the intention being to start out with a bit of tape over the top of each hole from the get-go.
The last three bands I played in used these McCallum oval-hole band chanters with Ross reeds, and the combination is great. As close to “plug in and play” as I’ve ever seen. Oftentimes no tape is needed. Go on YouTube and watch videos of the Los Angeles Scottish Pipe Band (Grade One) or LA Scots as they are also known, and you’ll hear what McCallum chanters with Ross reeds sounds like.