Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
Q:1/8=180
M:6/8
K:G
['G2 G', 'G2 B BdB BdB BAG']  
X:1
L:1/8
Q:1/8=180
M:6/8
K:G
|: D | G2 G G2 G | F2 E D2 F | G2 G G2 A | B3 d2 D | G2 G G2 G | F2 E D2 F | BdB AFD | E2 F G2 :: 
 D | G2 B BdB | BdB BAG | F2 A ABA | ABA AGF | G2 B BdB | BdB BAG | dcB AFD | E2 F G2 :|  