I first heard Horslips on a trip cross-country, while staying in Medford, OR- also, my first visit to this wonderful state. When I got back to the Cleveland area, I tracked down their album, "Book of Invasions," which had this song. While tracking down this clip, I found that they were still playing as recently as last year. Kinda like Jethro Tull, but more Celtic, more flute-centric, and more power rock. An obscure group that in a fairer world would have received more attention.
There's a live version here from 2011; I'm impressed with their polish playing live, but the sound quality/recording is too muddy for me to take.