Here is a suitable schedule. Note that there are two rounds with only three games, as the total number of games is not divisible by 4.
(---) (A G) (B J) (F I)
(D G) (C F) (E H) (A J)
(C D) (H J) (G I) (B F)
(A B) (H I) (F J) (D E)
(A F) (C J) (D I) (B G)
(A I) (F G) (B E) (C H)
(D F) (I J) (E G) (B H)
(B I) (A E) (C G) (D H)
(G J) (E F) (A H) (B C)
(E I) (D J) (A C) (F H)
(G H) (C I) (B D) (E J)
(C E) (A D) (B F) (---)
(C J) (E I) (D H) (F G)
(F H) (B E) (A I) (G J)
(C G) (B H) (F J) (A D)
(H J) (A F) (G I) (C E)
(D E) (G H) (B J) (C I)
(E F) (D G) (A H) (B C)
(I J) (B G) (C D) (A E)
(A B) (E J) (D F) (H I)
(B I) (A C) (E G) (D J)
(E H) (D I) (C F) (A G)
(C H) (B D) (A J) (F I)
