This is a picture of a full set of uilleann pipes belonging to a fellow piper, taken at our recent AZUPS gathering.
There are four common configurations for the Irish uilleann bagpipes: the practice set, half set, three-quarter set and full set. The practice set, though the name can be misleading, does not mean that it is used only for practice. This is just the configuration that most students of the pipes start out with and is a fully functioning instrument. The practice set consists of the bag, bellows and chanter. The chanter is the part that is held in the hands and contains the actual reed that sounds the notes when fingers are lifted (in layman’s terms, it is like a clarinet with a bag and bellows connected to it rather than a mouthpiece). A practice set is upgraded to a half-set by the addition of drones. There are three drones: the tenor, the baritone and bass, which play a single note, D, each at an octave below the last. We upgrade to a three-quarter set by adding the tenor and baritone regulators, which are the multiple brass keys you see in the picture. Regulators are used to pay chordal accompaniment to the melody of the chanter. As you can see, this is becoming increasingly more work for the piper to manage! A chord is played by placing the wrist on neighboring keys across the two regulators to sound two notes that create a basic chord. With a three-quarter set you only get a two chord note but with the addition of the bass regulator (thus making a full set) you get three-note chords.
So, to reiterate, the piper who plays a full set is performing the following functions simultaneously: pumping the bellows to fill the bag with air, squeezing the bag at the right pressure for the particular note being played (you have to squeeze harder as you play higher pitched notes and softer for the lower notes), moving the fingers to play the melody on the chanter, keeping the bag pressure adjusted correctly so that the notes of the chanter are in-tune and match the harmonics of the drones (attention must be paid to keep pressure steady so that the drones don’t waver in pitch), and finally, moving the wrist/edge of the hand up and down the regulators to provide chordal accompaniment. Whew!
If you’d like to see all this in action, check out this video: http://www.youtube.com/watch?v=AcsBVtbZ2ww&feature=fvw (if you don’t think you’ll have the patience to watch the whole performance, I recommend starting it at about 2:45 to see what the pipes can really do!)