Their current name is a partial translation of the Irish language terms píobaí uilleann (literally, "pipes of the elbow"), from their method of inflation.

The bellows not only relieve the player from the effort needed to blow into a bag to maintain pressure, they also allow relatively dry air to power the reeds, reducing the adverse effects of moisture on tuning and longevity.

If one tone hole is closed before the next one is opened, a staccato effect can be created, because the sound stops completely when no air can escape at all.

These enable the piper to play simple chords, giving rhythmic and harmonic accompaniment as needed.

He cited to this effect William Shakespeare's play The Merchant of Venice published in 1600 (Act IV, sc.

Essentially their design required the joining of a bellows under the right arm, which pumped air via a tube to a leather bag under the left arm, which in turn supplied air at a constant pressure to the chanter and the drones (and regulators in the case of the Irish Uilleann pipes).

The Pastoral and later flat set Union pipes developed with ideas on the instrument being traded back-and-forth between Ireland, Scotland and England,[2][9] around the 18th and early 19th centuries.

Only recently has scientific attention begun to be paid to the instrument, and problems relating to various stages of its development have yet to be resolved.

Certainly many of the early players in Ireland were Protestant, possibly the best known being the mid-18th-century piper Jackson from Co Limerick and the 18th-century Tandragee blind pipemaker William Kennedy.

[10] As late as the 19th century the instrument was still commonly associated with the Anglo-Irish, e.g. the Anglican clergyman Canon James Goodman (1828–1896) from Kerry, who had his tailor-made uilleann pipes buried with him at Creagh (Church of Ireland) cemetery near Baltimore, County Cork.

His friend, and Trinity College colleague, John Hingston from Skibbereen also played the uilleann pipes.

The instrument is most usually (nowadays) tuned in the key of D, a tradition begun by the Taylor brothers (originally of Drogheda, Ireland, and later of Philadelphia, Pennsylvania) in the late 19th century.

Up to then, most pipes were what would be termed as "flat sets" in other keys, such as D♭, C, B and B♭, tunings which were largely incompatible with playing with other instruments.

Chanters of around 362 mm (14+1⁄4 in) in length produce a bottom note on or near D4 (D above middle C) where A4 = 440 Hz, i.e. modern "concert pitch".

They typically have wider bores and larger tone holes than the earlier "flat" pitch sets, and as a consequence are a good deal louder, though by no means as loud as the Highland pipes of Scotland.

They were developed by the Taylors to meet the requirements of playing in larger venues in the United States; today they are the most common type of uilleann pipes encountered, though many players still prefer the mellower sound of the earlier style narrow-bore pipes, which exist in pitches ranging from D through D♭, C, and B down to B♭.

Equal temperament is almost universal with the fixed pitch instruments used in Irish music, which can clash with the tuning of the pipes.

A practice set consists of only the basic elements of pipe bag, bellows and chanter, with no drones or regulators.

This is an intricately made wooden cylinder tied into the bag (as any other stock) by a thick yarn or hemp thread.

The original design of the stock was a hollow cylinder, with two metal tubes running through it to both hold the regulators and independently supply air to them.

In the late 19th century it became more common to build the stock from a solid piece of wood, with five holes bored through it end-to-end.

These drone reeds were generally made from elderberry twigs in the past, while cane began to be used in the late 19th century.

Many airs end a section on a G or A in the first octave, at which point a piper will often play one of these hand chords for dramatic effect.

More rarely, a simple gravity- or spring-operated flap valve attached to the bottom of the chanter achieves the same end.

Generally, for all other notes (except for special effects, or to vary the volume and tone) the chanter stays on the knee.

A type of simultaneous vibrato and tremolo can be achieved by tapping a finger below the open note hole on the chanter.

Most uilleann chanters are very responsive to "half-holing" or "sliding", which is the practice of obtaining a note by leaving a fingerhole only half-covered.

With this technique and some practice, many pipers can accurately play the semitones which would otherwise require a chromatic key to be installed.