used in Irish traditional music
The Uillean pipes, the Irish version of bagpipes, are considered to be a most difficult instrument. It has a bellows which is pumped by one arm. The other arm applies pressure to a bag just pumped full of air, all while the fingers play melody on a chanter and simultaneously control the drone (the background "harmony" you may associate with bagpipes).
It is said of the instrument that it takes three times seven years to master it. Seven years to understand the instrument, seven years to learn the tunes, and seven years to put it all together.