Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
Q:1/4=140
M:4/4
K:G
['dBGB cAFA', 'A2 c2 B2', 'B2 Bc']  
X:1
L:1/8
Q:1/4=140
M:4/4
K:G
|: dBGB cAFA | G gfe d2 cd | dBGB cAFA | G2 B2 G4 :: A2 c2 B2 d2 | A2 c2 B2 d2 | A2 c2 B2 e2 | 
 dcBA G4 :: B2 Bc dcBA | B2 Bc dcBA |1 B2 Bc defg | dcBA G4 :|2 B2 Bc defg | dBcA G4 |]  