A5              G5 E5  A5 
O come, O come, Em-man-u-el
     C5             D5 G5   A5
And ransom captive Is---rael
     D5               C5 E5    G5
That mourns in lonely ex--ile here
   A5             D5  G5   A5
Un-til the Son of God a-ppear
   G5         A5      D5 G5    A5
Re-joice! Re-joice! Em-man-u-el
        C5           D5  E5   A5
Shall come to thee, O Is--ra-el.

This pattern follows throughout the song. Here are the rest of the lyrics.

O come, Thou Rod of Jesse, free
Thine own from Satan's tyranny
From depths of Hell Thy people save
And give them victory o'er the grave
Rejoice! Rejoice! Emmanuel
Shall come to thee, O Israel.

O come, Thou Day-Spring, come and cheer
Our spirits by Thine advent here
Disperse the gloomy clouds of night
And death's dark shadows put to flight.
Rejoice! Rejoice! Emmanuel
Shall come to thee, O Israel.

O come, Thou Key of David, come,
And open wide our heavenly home;
Make safe the way that leads on high,
And close the path to misery.
Rejoice! Rejoice! Emmanuel
Shall come to thee, O Israel.

O come, O come, Thou Lord of might,
Who to Thy tribes, on Sinai's height,
In ancient times did'st give the Law,
In cloud, and majesty and awe.
Rejoice! Rejoice! Emmanuel
Shall come to thee, O Israel.