Carol of the Bells

From Wikipedia:

“Carol of the Bells” is a popular Christmas carol, composed by Mykola Leontovych with lyrics by Peter J. Wilhousky. The song is based on a folk chant known in Ukrainian as “Shchedryk“. Wilhousky’s lyrics are copyrighted, although the original musical composition is not.  The song is recognized by a four-note ostinato motif.