Key  G
Chord Symbol  Melody ( )

D9  O'  (G)
Gmaj9  Come All Ye (G, D, G)
Am9  Faith-ful (A, D)
Bm9  Joy-ful and (B, A, B)
D9  Tri- (C )
Gmaj9 - -um-phant, O' (B, A, G)
Em7  come (G)
A9  ye O' (F#, E)
D9  co-ome ye (F#, G, A )
Bm7  to (B)
Em7  Beth (F#)
A7  eth-le (E, D)
D6  hem (D)
Gmaj9  Come (D)
Am7  and be- (C, B)
D9  hold (C)
Gmaj9  Him (B)
D7  Born the (A, B)
Em7  king (G)
Am7  of (A)
D7  Angels, O' (F#, E, D, G)
Gmaj9  Come (G)
Am7  let (F#)
Bm7  us (G)
D9  a- (A)
Gmaj9  dore Him, (G, D, )
D9  O' (B)
Gmaj9  Come let us a- (B, A, B, C)
D9  dore Him (B, A)
Ddim7  O' (B)
Am7  Come let us a  (C, B, A, G)
Bm7  dore (F#)
Em7  Him (G, C)
Am7  Chri(B)
D9  iist the (A, G)
G6  Lord (G)

This song has been recorded thousands of times, different arrangements from R&B (i.e. "Soul") to Country.
Perhaps you can come up with a good arrangement from this basic chord structure.