If your area of interest includes Irish traditional song, music and/or dance, then you need to darken the door of the wonderful Irish Traditional Music Archive at no. 73 Merrion Square. This amazingly comprehensive reference archive is also a treasure trove for anybody looking at Irish studies, history and folklore.
ITMA is open to the public 5 days a week and on 1 Saturday per month. Call in, or if you've a more in-depth query place a call in advance of your visit.