The trick being for you to tune to his A--keeping in mind that he should be good and warmed up before you do it.

I haven't played with anyone with those fancy modern pipes, but played a bit of Balkan music with Bulgarian/Macedonian gajde players--gajde being a much more primitive version of the instrument --best practice was to tune the guitar to an open tuning that featured the fundamental and drone notes of the pipes and work from there.

What really worked was to hang everything else up and let the piper play with the drummer--next best was to ask the gajde player to play his shephard's flute/kaval instead;-)