Okay, I'm typing this artist's comments for the third time. As such, I am going to shorted this so that I do not loose the little sanity that I have left.
Hymn is inspired by and written to the tune of Coventry Carol. While the subject matter of the songs are similar, the reasons for the songs are completely different.
Coventry carol is, according to legend, the last song that mothers of the tribe of Israel sang to their children before King Harod's men came and killed all of the babes ages two and under in an attempt to keep the new "king" that the Magi told him about (and then wisely avoided telling him where he was).
Hymn for the Lost Children is about a period in Abintran history when any and all children with magic were killed, or at the very least sent out of their villages to be killed. After the Order lost the Witch Wars the Kirnblites went back and attacked the villages that had sided with the Order again, carrying off anyone with any hint of magical power, and vowed to return when more were born. To make sure that this did not occure, any and all children displaying magic were sent down the river that runs the length of the Vale (later known as the Dark Lands) to be drowned in the sea. The "lucky" ones actually made it to the sea (and were hopefully were rescued by the underwater community.) The not so lucky ones were sold to the Kirnblites. As the song describes, though, the children were taken off in the middle of the night to the river to be shipped off.