I’m referring to Paddy Keenan - I was listening to Avalon from Na Keen Affair and was completely bamboozled by the way he swoops down the scale around b and a - I’ve heard him do it live so i know it’s not some kind of studio enhancement - perhaps this thread could invite others to offer exmaples of piping where you’re completely at a loss to work out how the piper has achieved the sound they produce - by the way i’m a lapsed piper hoping to get back into it soon - wish me luck!
Good topic There are some techniques I have questions about as well but one at a time.
This one reminds me of the man holding a violin case that finally flags down a cab in New York.
Upon entering the taxi he says to the cab driver, “quick whats the fastest way to Carnegie Hall”?
Says the driver, “practice, practice, practice” 
Well this one reminds me of a man holding a set of pipes and if he knew the mechanics of the technique it would be easier to perfect. 
Keenan freefalling…
This may be relevant. Watch John McSherry on the doinna video on U tube. He puts vibrato on the b using the bottom finger of his top hand this moves the note towards b flat, when this finger is on the chanter a b flat is produced this may be the start of Keenan’s slur
Might this simple theory be true?:
The Paddy Keenan freefalling goes from around C or D down through B to A or even to G. He might just use the C key. In such speeds a crossfingered C and a keyed C in the lower octave wont make a difference. He might just tap the C key when playing a B, splitting up the B note, making it two notes, without changing fingering…(?)
that technique is nothing…
what you want to hear Keenan do is ‘The High Level’ on the ‘Cornemuses d’Europe en Cornuaille’ double CD from France(1990? 91?).
Figure out what’s going on there, an you’ll be onto something!
here’s that disc’s call #'s:
‘A Celebration of pipes in Europe’
‘Cornemuses d’Eurpoe en Conrouaille’
Keltia Musique KMCD18
1990, 2 disc set
He does use the Cnat key quite a lot in fast passages, but I was never able to figure out what he was doing with it!
There’s no mystery to Paddy’s glide from B down to A, which seems to be a favourite of his as he does it quite a bit.
You simply reverse the finger motion that you do when you glide from A to B.
It takes some practice to get smooth, but is not at all difficult.
About Paddy’s party piece hornpipe, I have four or five recordings of him playing that (the CD you mention, another CD, and two or three bootleg tapes) and I’ve transcribed the version that to me seemed the most coherent. It has quite a bit of backstitching.
yeah there’s some really worthwhile licks in there…
especially those ascending arpeggiated chordal triplets in the 3rd part of High Level…yum!
tremendously difficult (for me) is the stuff he does going in & around the ‘break’: popping effortlessly between lo A and hi E, for ex…
the ‘secret’ about that slide panceltic mentions, is to keep the left long finger on the chanter while playing B, then simply roll it down for the A…very much a ‘slowhand’ movement…