Celtic folk music is the umbrella for traditional song and dance-tune practices from the Celtic-speaking regions, especially Ireland and Scotland, and also Wales, Brittany, Cornwall, and the Isle of Man. It features modal melodies (often Dorian and Mixolydian), distinctive ornamentation, driving dance rhythms, and a strong oral/aural transmission tradition.
Typical instruments include fiddle, flute, tin whistle, uilleann pipes or Great Highland bagpipes, Celtic harp, bodhrán, button accordion/concertina, and later accompaniment by guitar and bouzouki (often in modal tunings like DADGAD). Common tune types are reels (quick 4/4), jigs (6/8), slip jigs (9/8), hornpipes (dotted 4/4), polkas (2/4), strathspeys (with the “Scotch snap”), marches, and slow airs. Songs may be in English, Irish, or Scots Gaelic (and in Brittany, Breton), covering themes from love and emigration to work, history, and myth.
As a modern genre category, Celtic folk music cohered during the mid-20th-century folk revival, which foregrounded regional traditions on stages and recordings while retaining the social, participatory essence of sessions, ceilidhs, and fest-noz gatherings.