Sometimes there are issues with drones that will have you scratching your head. I knew one 
bagpipe by a well-respected old Edinburgh maker, where one tenor drone would change octaves right at that point where it came into tune with the chanter and other drones. In sorting this problem out, I discovered that the bore of one tenor bottom section was significantly larger than the other. When I swapped in a bottom section with a “normal” size bore, the problem disappeared.
Now whether it left the shop as such or someone had been up inside over the years I can’t say. I do know it was necessary to sleeve the bore to settle the bagpipe down.
I’ve known other bagpipes that are loud and coarse sounding. Sometimes the issue is with the size of the bushing bore. Once the bore is reduced, the both sound and behavior improves.
I do not recommend radical experimentation unless you are highly skilled, both as a piper and in machining. In my experience, there are no guaranteed results. If you have a drone that is rough sounding, or has excessive “growl” I would first experiment with various reeds to minimize or eliminate the problem. If the problem cannot be corrected within your own abilities or reach thereof, I would be inclined to abandon the drones in favor of a better performing set.
There are many tales of drone designs or flaws having an impact on drone performance. One of the silliest is that manufacturers strive for a rifling effect, to twist the air as it ascends the drone. Rubbish! (Scottish terminology for “bull”) Any such marking on a drone is accidental scoring due to faulty tooling or workmanship.
Jim Tweedie was perhaps the first maker to polish his bores and indeed, his drones remain magnificent to this day.
The inside bore should be smooth, without checks, burrs, chips, chatters, or uneven walls. I once owned a bagpipe where the bores within the tuning chambers were tapered rather than parallel. Aside from being a pain to move up and down on the tuning pin, the drones were incredibly unsteady. Ed Neigh had a similar experience with sets of pipes within the City of Guelph Pipe Band. He tried everything to sort out the problem and ended up abandoning those bagpipes altogether.
Modest roughness in the inside bore may or may not present a problem. If one is so inclined, the bore can be polished smooth. I should warn that any attempts to alter the inside of the drone can severely damage the drone, requiring costly repair or replacement. I am aware of one individual that split his Henderson drone in such an attempt.
I like to give the bores a healthy dose of bore oil in advance of any polishing. I rig a wire probe with “000” grade steel wool wrapped around the probe end and doused in bore oil. I insert the other end of the probe in a hand held power drill and gently, slowly, ease the probe through the entire length of the section in hand. You can best judge your progress by how much resistance the probe is experiencing. If the resistance is too great, you can damage the bore or split the drone. It’s better to start with a small amount of steel wool and increase a few strands at a time until the desired tension is felt and enough pressure is created to burnish the oil into the Blackwood. Cautiously following this method, you can polish most bores to a shiny, smooth finish.
Sometimes, tuning chambers will wear unevenly or they have been bored incorrectly by the maker. You will notice that the hemped tenor does not move smoothly and evenly through the tuning chamber. It is inclined to be tight in one spot and loose in another. If this becomes a problem, they should be entrusted to a professional bagpipe maker for re-boring. This is not a job for an amateur or for amateur tools.In order for drones to perform at their peak, the top section of bass and tenor drones should be fully extended to the bottom of the hemp line on the tuning pin. This allows for the greatest use of the tuning chamber, producing full resonance. Quite noticeably, the same drone, differently addressed to tune low on the tuning pin, will sound dull and lifeless. With the bass drone, the top section should tune right at the hemp line. Once set, there is no need to move this section. The mid-section may tune quite low on the bottom section tuning pin. If you’re having issues with the bass drone double-toning, adjust your bass drone reed to allow the mid-section to tune lower. Two-fingers is the accepted normal tuning position.
Some bass drones will growl, generally due to the bore of the bottom section being too large. Swapping out a section with a smaller bore will probably remedy this issue.
All reeds, both cane and synthetic, can be adjusted to sound and perform to a wide range of choices. Most drones today will readily accept reeds without the fickle nature of some older sets of pipes. The basics of reed design are pretty much universal. A narrow, short reed body will produce a sharper pitch. A shorter, lighter tongue will do likewise.
The bottom line…Know your bagpipe and know your reeds. Listen, listen, listen, not only to your bagpipe but also to other bagpipe. Ask lots of questions. Your issues may be reduced or eliminated through reed selection or adjustment. If not, you may have to call in the big guns!
