There seems to be a growing interest in Celtic spirituality in today’s churches. And for good reason - there is a deep history of mysticism growing out of the rugged hills and foggy shores of Ireland and Scotland. There’s great artwork and romantic stories. And of course, there’s the music.
For a long time, I had a Celtic music group at my church. We played almost every Sunday. Usually we’d play the obbligato parts on a Taizé song at communion, then maybe a closing hymn, and close with a jig or reel for a postlude.
Most violinists will relish the opportunity to play fiddle tunes. Don’t worry - fiddle and violin are really the same. Flutes and recorders sound great in an Irish band too, although they almost always have to transpose up an octave. Guitar and other strummed instruments would also be appropriate. Accordion has the advantage of being a bass instrument, a chording instrument, and a melody instrument all in one. It’s also a sustaining instrument like the organ, so it works well for congregational song. Piano is commonly seen as a rhythm instrument in Celtic bands, but I would encourage more organists to learn accordion - it’s an easy instrument to learn. And if you can get a percussionist to learn bodhran (pronounced “BOW-ron”), the traditional Irish hand-drum, you’ll have a really great ensemble.
One of my challenges with traditional Celtic music is to stop thinking in terms of Basso Continuo (bass and chording instruments accompanying melodic instruments). If you listen to traditional Celtic groups, you will never hear a bass line. Even chording instruments like guitar are optional for a fast reel or a mournful tin whistle solo. That said, be sure to have some bass when leading congregational singing - even my little accordion does the trick.
Other than the Taizé music I mentioned above, we also played a variety of hymns. Anything folksy (BUNESSAN), Celtic (SLANE), or early American (HOLY MANNA) works quite well. The key is to slow down the harmonic rhythm: one or two chords per measure. If you play four chords per measure out of the hymnal on the piano with your instrumentalists it will sound Lutheran instead of Irish!
Irish bands like the Chieftains are famous for playing jigs, reels, and hornpipes. I found that my congregation loved it when we played a jig or two for the postlude. Traditionally, instrumentalists learn tunes by ear while sitting in the village pub; I decided to buy sheet music instead. The most useful was English Country Dance Tunes, which has a variety of difficulty levels. To extend these very short tunes, simply string together two or three in related keys (but identical time signatures). If you listen closely to The Chieftains or The Dubliners, you’ll hear this is exactly what they do.
Finally, remember: the Boston basketball team name is pronounced with a soft “c”, but anytime you refer to Celt culture, use a hard “c.” Forget that, and you’ll have some angry Irishmen on your hands!