The 17 minute mark in the first video marks the end of the song
“ALL THE WORLD WILL BE JEALOUS OF ME”. 1917
Rock of Ages comes later.
The tune in the second clip is the familiar Christmas carol
Les Anges Dans Nos Campagnes (Angels in our plains, aka Angels We Have Heard on High. As has been mentioned before on this thread, the one from "The Human Comedy" sounds like "Now the Day Is Over" by the great English hymnodists Sabine Baring-Gould (who co-wrote "Onward, Christian Soldiers") and Joseph Barnby (who composed "Oh Perfect Love").