A Welsh lullaby. This and other autoharp Christmas music arrangements at: http://www.specialteesmarket.com/autoharp-music/autoharp_christmas.html Here's some Wikipedia info: Ar Hyd y Nos (English: All Through the Night) is a Welsh folksong sung to a tune that was first recorded in Edward Jones' Musical and Poetical Relics of the Welsh Bards (1784).

Reportedly the first song written by Turlough O'Carolan (1670-1738) at the suggestion of Squire Reynolds. The subject was a battle between two hills controlled by rival Fairy Kings. This version on diatonic autoharp.