The Irish Harmonica
THE harmonica, more popularly known as the mouth organ, got left behind in the Irish music revival of the late 1950s. In the session it lacked volume and created something of a rattling effect. However, it gained a new profile in 1994 when the mastery of Brendan Power gave the instrument a new prominence with the release of his New Irish Harmonium album.
In Irish music the diatonic harmonica is usually called the mouth organ and the chromatic is referred to as the harmonica. The diatonic is suitable for jigs and reels, although among the newer players, Mick Kinsella prefers to play reels on the chromatic. The tremolo is now widely used as well, having been popularised by the Murphy family of Wexford. 
Folk singer Andy Irvine has always used the harmonica for accompaniment, worn about his neck Dylan-style. His harmonica can be heard to great effect on Christy Moore's early Prosperous album, but also with Sweeney's Men and on his later solo releases.
While not widely used in the Irish music session, the instrument has been growing in prominence since the mid-1990s.
Eddie Clarke, originally from Virginia, Co Cavan, plays the harmonica in a highly ornamented style. In 1981 he released an album Crossroads with Clare fiddle player Joe Ryan. And Noel Battle from Mullingar is a 12-times All-Ireland champion on the harmonica.
But, not for the first time, an instrument's advance in Irish music happened abroad - this time in New Zealand.
Brendan Power hails from Nelson and moved to London in 1992. His stylistic innovations and impressive ability on the harmonica attracted renewed interest in the instrument with the launch of New Irish Harmonium.

The Murphys of Co Wexford - John and Pip and their late father Phil, are strong exponents of the harmonica in Irish traditional music.
Meanwhile Mick Kinsella has been playing harmonica since about 1985. He rose to prominence in 2000 with the launch of his eclectic CD On the Fiddle. With a background on drums with showbands, he was influenced by Dublin blues player Don Baker and then Rick Epping and Eddie Clarke.

California-born Rick Epping moves between Ireland and the United States. He plays harmonica, concertina and jaws harp. He often plays the harmonica and concertina at the same time, notably on the 2009 album Music from the Atlantic Fringe (website) with Cathy Jordan and Seamie O'Dowd, both of Dervish.

Like Brendan Power he is also a very good player of other musical styles. He played with Brendan Power and Rick Epping on the "Triple Harp Bypass" tour. He has also taught at the harmonica school run by Waltons in Dublin.

Although born in New Waterford, Cape Breton, Tommy Basker (1923-99) played Irish harmonica, as did his father. He played in Boston with accordionist Joe Derrane. He used the throat more than the tongue to create embellishments.
Donegal-based Tom Byrne brings jazz, classical and blues to his unique interpretations of Irish tunes and exhibits the steady progress being made by the harmonica in Irish music.
Other players of note are Austin Berry, Rory O Leoracháin, Joel Bernstein, Tom Clancy and Paul Moran from Galway.

Harmonica Links
Irish Harmonica
For a technical understanding of the mouth organ and harmonica in Irish traditional music, read harmonica player Rick Epping's excellent article.
http://www.irishmusicreview.com/harmonicadiscography.htm Brief biographies of Irish harmonica players
http://harmonica.co.uk - website of the National Harmonica League

Brendan Power website

Irish and American Fiddle Tunes for Harmonica, by Glen Weiser.
Andy's Front Hall. Good source in New York for books and instruments.
Society for the Preservation and Advancement of the Harmonica
Traditional Mouth Organ. Book and CD or tape from the reliable "Sully" of Halsaw Music.
Mick Kinsella interview: Lots more technical stuff about playing Irish music on the harmonica.
Celtic Harmonica Discography. Broad selection of harmonica music CDs.
Larry Adler The Free Reed interview
Donald Davidson. Traditional Scottish mouth organ player.
Tommy Byrne's website