Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
Q:3/8=104
M:6/8
K:G
['D G2 e d2 c ded cBA', 'ABA E2']  
X:1
L:1/8
Q:3/8=104
M:6/8
K:G
"^A" D | G2 e d2 c | ded cBA | GFG ABc | d2 B G2 :|"^B" G | ABA E2 E | ABA E2 D | GFG ABc | 
 d2 B G2 :|  