I do not play the uilleann pipes but as my family has been making them for more than 25 years, I do have a practice understanding of the pipes and bellows.
I personally do not like seeing a uillean piper hacking away on their bag like they are chopping wood. To me it gives the feeling of urgency like when a GHB player plays with a small bag and many short breaths.
Aesthetically it is also not pleasant on the eye. To the ear, the music is flowing yet, to my eye the piper’s actions look desperate and urgent, especially with plaintive tunes.
This girl can play the chanter and has good bag control but looks like she is chopping wood with her bellows arm, flapping like a seagull, and then that great thump just as she takes up the slack.
https://www.youtube.com/watch?v=P40YOU8ggJk
The bloke in this video looks like he is relaxed and not rushed at all with his bellows arm. No flapping like a seagull and he does not appear to hit an urgent stop once he has taken up the slack.
https://www.youtube.com/watch?v=gfhbik61V20
The answer is in the design of the bellows.
Note how Calum Stewart uses a straighter sided tear-drop bellows design and the size, (capacity) of the bellows is larger than conventional teardrop designs. The straighter sides remove much of the excess leather so the slack is much reduced, there is your answer.
We make extended hexagon (coffin) shaped bellows and there is almost no slack to take up. We strongly recommend this design for learners because of the small slack and larger capacity. Like with the GHB pipes, the transition from squeeze to blow is where there is the greatest potential for error, so fewer breaths mean fewer chances for error. No different on the uilleann, especially on the second octave.
With the better designed bellows, you are pumping less times per minute because of the larger capacity and because you are not hacking at the bellows to get to the take-up point, the right hand is able to remain more stable because there is no jerk from the take-up and no sudden stop to put pressure on the right wrist and fingers.
We have never had a piper try the extended hexagon bellows and state that their teardrop design bellows was better, never!
For anyone interested in the exact specs and materials, Murray is very open and obliging with his specs and if you look at his videos, you will see the difference immediately. As he makes the pipes and reeds and plays most weeks in a pub band, he is better suited than I to give information from the player’s perspective. His email, murrayjackson@xtra.co.nz
Cheers
G