"All You That in This House" Christmas sheet music is a beautiful minor melody with 10 verses of Christmas song lyrics that will remind you of a Wassail song, with its jovial celebration of eating and drinking! Download it free in 4 different keys.
Irish tin whistle is the perfect instrument for this melody:
This Christmas song can also work as a round, though there are some almost-dissonant spots (not unpleasant, but perhaps requiring a bit of focus on the part of the singers!).
I first ran across this song in Mel Bay's A Celtic Fiddle Christmas.
This fun fiddle book is full of familiar and unfamiliar Celtic songs, about half of which are duets, and some rounds. They are pretty easy, being in first position. Some have engaging names such as "The Furry Day Carol." The Christmas sheet music "All You That in This House" I had never heard before, but I found it catchy immediately, and fun to play on the violin.
Because the second and third phrases sound the same, I would wait until halfway through the melody before starting the second voice, and probably only use two parts.
Here's a funny little version of this English carol which employs an updated sound:
If you are interested in an accompaniment more complicated than a single chord, try going back and forth between the i and iv chords -- that is, the 1 & 4 chords. (For those of you new to chord theory, the major chords -- usually the I, IV, and V -- are written with capitol letters, and minor chords are generally shown with small-case letters. Here in this song, the i and iv are minor.)
So, to work that out, it would be Bm and Em in the key of Bm; Cm and Fm in the key of Cm, Dm and Gm in the key of Dm, and Em and Am in the key of Em. Have fun!