I saw the Chieftains play last night. Paddy Moloney accompanied a Mexican band playing his drones on their own. Does that mean they were playing and singing in D? He also accompanied on the chanter on and off, mostly on, Ry Cooder, a Scottish pipe band, Scottish singers, Mexican song and “I cant get no satisfaction”. Can anyone give me an explanation as to how it is done. Thanks
If he plays on a regular D set then the singers should definitely be singing in D. Maybe G, at a pinch. And if they didn’t, you would’ve notice that it would’ve sounded very strange and dissonant. As for the chanter, it’s hard to tell without an audio/video sample, but he would probably either be playing some sort of harmony to the vocals, or moving between notes of the chords to the song in question, or he just might be emphasising important notes in the melody, but obviously the chanter is incapable of supplying full chordal backing for a singer, which would only be doable with regulators.
Paddy Moloney has a gift for harmonising. 2 years ago there was a TG4 program about him (it’s available on YouTube in several parts) in which he and Barney play a duet on the whistles. Towards the end, Paddy broke off and played a line of harmony against Barney’s main melody. Barney described Paddy as “a Hoor for Harmonies”! In the same program he also did a duet on pipes with Kevin Rowsome in which Kevin played Six Penny Money and Paddy played a line of harmony all the way through. Outstanding!
As a great piper once said “You just play the feckin’ things!” 
Patrick.
Yes Paddy is brilliant at improvising harmony parts/descants.
If you go back and listen to those old Chieftans albums you’ll hear how, usually, the fiddles and flute are assigned to the melody, giving Paddy the freedom to improvise.
Listen closely and you’ll hear all kinds of amazing crazy things. Very often he’s not playing anything remotely resembling the tune: popping and trilling all through a part of a jig or a reel, playing random long low notes during the high part of a tune, etc etc.
But yes since he’s using a D chanter the tunes will have to be in one or two sharps, G major and D major and the related minors. BTW for studio work the pipes like G better than D because the C# tends to flattness while the C natural is usually in tune. I have to use extra pressure on C# to bring it up to pitch.
His whistle duet with Sean Potts playing Banish Misfortune on Chieftains 2 is a great example of this.