Pressure stability?

Something approaching pressure stability is occurring in my piping. The drone's getting more constant, and I'm getting better at timing my use of the bellows to fill the bag at opportune moments. It seems - although this may turn out to be a delusion on my part or just a compensation for bad technique - that the way to go is to avoid refilling the bag on long chanter notes, because then any pressure fluctuation is significantly more audible than it is when the chanter's changing notes, partly because I'm also getting the hang of the idea that some notes seem to require slight pressure variations anyway.

That latter might be down to having a hire set of pipes that's presumably not in the best of condition, but given my experience with the recorder it seems that anything using a tube of differing lengths with discrete fingerings is going to require pressure variations to get the temperament right throughout the range.

Which perhaps answers why the high A is so sharp and unpleasant. Time will tell... that not's so extraordinarily unpleasant that I'm readily willing to believe in a minor chanter defect of some sort.