Formulate chord combinations to increase the harmonic complexity of the specified musical excerpt.
"^Cantabile" D | D E F G2 B | A F A d3 | f3/2 g/ f e2 d | e f e c B A | 
 D E F G2 B | A F A d3 | f3/2 g/ f e2 d | e3- e2 :: f/g/ | 
 a2 A d2 c | B2 g e3/2 d/ c | d2 c B2 A | G2 e c3/2 B/ A | 
 f3/2 g/a/b/ g2 f | e3/2 f/g/a/ f2 e | d3/2 e/f/g/ e2 d | d3- d2 :|  
X:1
L:1/4
Q:1/4=120
M:6/4
K:D
"^Cantabile" D |"D" D E F"G" G2 B |"D" A F A d3 |"D" f3/2 g/ f"G" e2 d |"Em" e f e"A" c B A | 
"D" D E F"G" G2 B |"D" A F A d3 |"D" f3/2 g/ f"E7" e2 d |"A" e3-"A7" e2 :: f/g/ | 
"D" a2 A"Bm" d2 c |"G" B2 g"A" e3/2 d/ c |"D" d2 c"Bm" B2 A |"Em" G2 e"A7" c3/2 B/ A | 
"D" f3/2 g/a/b/"G" g2 f |"Em" e3/2 f/g/a/"A7" f2 e |"G" d3/2 e/f/g/"A7" e2 d |"D" d3- d2 :|  