Friday, December 19
qui stas in signum populorum,
super quem continebunt reges os suum,
quem gentes deprecabuntur:
veni ad liberandum nos,
jam noli tardare.
O Root of Jesse,
who stands as a sign for the people,
kings stand silent in your presence,
whom the nations will worship:
come to set us free,
put it off no longer.
Find the chant notation here.
Also have a look at Fr. Tucker's post on the various antiphons and settings.