This is the Icelandic music group Árstíðir, singing in a train station in Wuppertal, Germany. “Heyr himna smiður” (“Hear, Smith of Heavens” in English) is a 13th century Icelandic hymn.
Historical info on the song:
“Heyr, himna smiður” was written by Kolbeinn Tumason in 1208. The music was composed in the 1970s by Þorkell Sigurbjörnsson (1938-2013), one of Iceland’s foremost contemporary composers.
Here are the translated lyrics:
Hear, smith of the heavens,
what the poet asks.
May softly come unto me
thy mercy.
So I call on thee,
for thou hast created me.
I am thy slave,
thou art my Lord.
God, I call on thee
to heal me.
Remember me, mild one, (or mild king. This is a pun on the word mildingur).
Most we need thee.
Drive out, O king of suns,
generous and great,
human every sorrow
from the city of the heart.
Watch over me, mild one,
Most we need thee,
truly every moment
in the world of men.
send us, son of the virgin,
good causes,
all aid is from thee,
in my heart.