Celtic rock sits Irish and Scottish traditional melodies and dance rhythms on top of a standard electric-guitar / bass / drums / keyboards rock band. If Celtic punk is the trad-plus-rock fusion coming from the punk side after 1982, Celtic rock is the same fusion coming from the prog and hard-rock side of the early 1970s. Fiddle and pipes sit at the same level of prominence as the guitar solos; songs run five to eight minutes; whole albums tend to concept themselves around Irish mythology or Celtic history. The Waterboys' 'Big Music' of the mid-1980s is a spacious, anthemic descendant of the same lineage.

Horslips, formed in Dublin in 1970, is the origin point. Their 1972 debut Happy to Meet, Sorry to Part figured out how to move jigs onto a rock rhythm section, and 1973's The Táin adapted the Old Irish epic Táin Bó Cúailnge (the cattle-raid of Cooley) as a concept album. The 1976 The Book of Invasions continued in Irish mythology. In parallel Thin Lizzy did 'Whiskey in the Jar,' Clannad did 'Theme from Harry's Game' (1982), and Enya's Watermark (1988) split ambient-Celtic off as its own strand.

Horslips' 'Dearg Doom' (1973) shows the prototype clearly: a high-speed reel driven by distortion guitar and Hammond organ, with the 6/8 jig feel supported by 4/4 rock drums, producing a polyrhythm you can hear consciously. The Waterboys' 'Fisherman's Blues' (1988) sets Steve Wickham's fiddle and Mike Scott's distorted acoustic guitar as equal front-line instruments — the widest and most open sound in the tradition. Runrig sang in Scottish Gaelic, and even without knowing a word the consonantal weight of the language gives the vocal an audible foreignness.

Horslips' The Táin (1973) — the record on which the whole idea was invented, still the essential entry. The Waterboys: Fisherman's Blues (1988) for the West-of-Ireland-in-1988 atmosphere. Clannad: Magical Ring (1983), which contains the full 'Theme from Harry's Game.' Runrig: Heartland (1985). Late-night listening, loud speakers, dim room.

The band name Horslips is a deliberate misspelling of 'horse hoof,' picked out of the air by leader Barry Devlin in a picture-disc printer's studio. The Waterboys' Fisherman's Blues sessions produced over a hundred recorded tracks in more than a year before being cut down to twelve songs. Mike Scott lived in Sligo during the sessions and reportedly read W.B. Yeats aloud daily. Runrig were the last generation of full-time musicians for whom Scottish Gaelic was their first language; their 2018 retirement was widely written up as the effective end of the Gaelic-language rock era.