There are many instruments that are commonly found played by folks playing Irish music be it at music sessions or performances by bands. Many are common to the various genres of folk music like the fiddle, guitar, keyboard accordion, keyboards, etc. Below we feature instruments are unique to Irish music.

Irish Tenor Banjo

The Irish Tenor Banjo first became popular in traditional Irish music from the 1920s. It made its way to Ireland from the American dance hall scene where it was mostly used as an accompaniment instrument.

Players would play chords and strum it in a similar fashion to a guitar. Irish musicians soon began to adapt its use to play the melodies of traditional tunes instead.

It wasn’t until the revival of traditional Irish music from the 1960s and 1970s however that the banjo started to gain the popularity it still holds today. This is due in large part to the influence of the iconic players Ronnie Drew, Barney McKenna and Tommy Makem.

Today the Irish tenor banjo is an important part of any céilí band lineup and commonly found at any good session. Banjo playing in Ireland has been revolutionized in the hands of a wealth of masterful players including Kieran Hanrahan, Gerry O’Connor, Mike Moloney and Enda Scahill.

Irish Bouzouki

The Irish bouzouki (Irish: búsúcaí) is an adaptation of the Greek bouzouki (Greek: μπουζούκι). The newer Greek tetrachordo bouzouki (4 courses of strings) was introduced into Irish traditional music in the mid-1960s by Johnny Moynihan of the folk group Sweeney’s Men, who retuned it from its traditional Greek tuning C³F³A³D⁴ to G²D³A³D⁴, a tuning he had pioneered previously on the mandolin. Alec Finn, first in the Cana Band and subsequently in De Dannan, introduced the first Greek trichordo (3 course) bouzouki into Irish music.
In the early 1970s, Andy Irvine, who was a member of Sweeney’s Men with Johnny Moynihan, gave a Greek tetrachordo bouzouki to Dónal Lunny, who replaced the octave strings on the two lower G and D courses with unison strings, thus reinforcing their lower frequencies. Soon after, on a visit with Irvine to the workshop of luthier Peter Abnett, Lunny commissioned a 4 course bouzouki with a three-piece, partially staved back. This was the first bouzouki built specifically for Irish music. Since then, the instrument has been adapted by many instrument builders for Irish traditional and other styles of folk music.
Wikipedia

Button Accordion

Unlike comparable instruments used in other American and European music genres, the two rows are tuned so that just a semi-tone separates them. This means that the melody of the tune can be played chromatically. Generally speaking, the most popular tuning combinations are the B/C and the and C#/D. An instrument tuned to B/C is ideal for a more fluid style of playing, such as that made popular in the 1940s and 1950s by the Tipperary-based musician Paddy O’Brien and subsequently Sonny Brogan and Joe Burke in the 1950s and 1960s. Dublin-born James Keane transported the instrument across the Atlantic, where he used it during his important performing and recording career.

Other notable proponents of the B/C version include Bobby Gardiner, James Keane and Finbarr Dwyer. Conversely, the the C#/D model is far more suited to a rather edgier and more punchy style such as the wonderful Kerry polkas. Over the course of the 1950s, the Button and Piano Accordion became increasingly popular among traditional Irish musicians and continues to be so today. It had become synonymous with traditional music. This model is known for its superior fluency, better range and greater ease when changing from one key to another, and they are pivotal in the line-ups of all truly great Scottish and Irish Ceili bands.
Source

Resources for Button Accordion players
Journey into tradition : a social history of the Irish button accordion

Uilleann pipes

The uilleann pipes Irish: [ˈɪl̠ʲən̪ˠ]), sometimes called Irish Bagpipes, are the characteristic national bagpipe of Ireland. Earlier known in English as “union pipes”, their current name is a partial translation of the Irish language terms píobaí uilleann (literally, “pipes of the elbow”), from their method of inflation. There is no historical record of the name or use of the term uilleann pipes before the 20th century. It was an invention of Grattan Flood and the name stuck. People mistook the term ‘union’ to refer to the 1800 Act of Union; this is incorrect as Breandán Breathnach points out that a poem published in 1796 uses the term ‘union’.

The bag of the uilleann pipes is inflated by means of a small set of bellows strapped around the waist and the right arm (in the case of a right-handed player; in the case of a left-handed player the location and orientation of all components are reversed). 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. Some pipers can converse or sing while playing. The bag which the bellows fill is clamped under the other elbow, which squeezes the bag to control the flow of air to the reeds (which make the notes).

The air goes from the bag to the chanter, drones, and regulators. The chanter is played with the fingers like a flute. The chanter has a range of two full octaves, including sharps and flats (because, unlike most bagpipe chanters, it can be overblown to produce the higher octave). The chanter is often played resting on the piper’s thigh, closing off the bottom hole, so that air can only escape through the open tone holes. 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. The three drones are simple open pipes; they constantly play three notes spread an octave apart. The three regulators are closed pipes. Untouched, they do not sound, but they have keys that can be opened by the piper’s wrist action (or hand, if they take one hand off the chanter).[5] Each regulator key sounds a different note when opened. The regulator keys are aligned so that several may be pressed simultaneously. These enable the piper to play simple chords, giving rhythmic and harmonic accompaniment as needed. There are also many ornaments based on multiple or single grace notes.

The tone of the uilleann pipes is unlike that of many other forms of bagpipes. They have a different harmonic structure, sounding sweeter and quieter than many other bagpipes, such as the Great Irish warpipes, Great Highland bagpipes or the Italian zampognas. The uilleann pipes are often played indoors, and are almost always played sitting down.

Bodhrán

The bodhrán is a frame drum used in Irish music ranging from 10–26 inches in diameter. The sides of the drum are 3 1⁄2 to 8 inches deep. A goatskin head is attached to one side (synthetic heads or other animal skins are sometimes used). The other side is open-ended for one hand to be placed against the inside of the drum head to control the pitch and timbre.

In some instances, one or two crossbars, sometimes removable, may be inside the frame, but this is increasingly rare on modern instruments. Some professional modern bodhráns integrate mechanical tuning systems similar to those used on drums found in drum kits. It is usually with a hex key that the bodhrán skins are tightened or loosened to set the pitch and adjust for atmospheric conditions.

Irish Flute

The Irish flute is a conical-bore, simple-system wooden flute of the type favored by classical flautists of the early 19th century, or to a flute of modern manufacture derived from this design (often with modifications to optimize its use in Irish Traditional Music, Scottish Traditional Music or Music of Brittany and other Celtic nations). The majority of traditional Irish flute players use a wooden, simple-system flute.

The simple system, transverse flute which plays a diatonic (Major) scale as the tone holes are successively uncovered. Most flutes from the Classical era, and some of modern manufacture include metal keys and additional tone holes to achieve partial or complete chromatic tonality. Due to its wooden construction, characteristic embouchure and direct (keyless) fingering, the simple system flute has a distinctly different timbre from the Western concert flute. Most Irish flute players tend to strive for a dark and reedy tone in comparison to classical flautists. Though most commonly pitched in the key of D, simple system flutes are available pitched in other keys, and are often heard in Irish music pitched in E flat, B flat and C. Although referred to as a D flute, this is a non-transposing instrument, so if you finger C, a concert-pitch C is sounded. The name D-flute comes from the fact that the simplest 6-hole wooden flute has D as its lowest note and plays the scale of D without any cross-fingering. The E-flat, B-flat and C versions are transposing instruments.

Irish Tin Whistle (Penny Whistle)

The tin whistle, also called the penny whistle, is a simple six-holed woodwind instrument. It is a type of fipple flute, putting it in the same class as the recorder, Native American flute, and other woodwind instruments that meet such criteria. A tin whistle player is called a whistler. The tin whistle is closely associated with Irish traditional music and Celtic music. Other names for the instrument are the flageolet, English flageolet, Scottish penny whistle, tin flageolet, or Irish whistle (also Irish: feadóg stáin or feadóg).The tin whistle, also called the penny whistle, is a simple six-holed woodwind instrument. It is a type of fipple flute, putting it in the same class as the recorder, Native American flute, and other woodwind instruments that meet such criteria. A tin whistle player is called a whistler. The tin whistle is closely associated with Irish traditional music and Celtic music. Other names for the instrument are the flageolet, English flageolet, Scottish penny whistle, tin flageolet, or Irish whistle (also Irish: feadóg stáin or feadóg).