Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:6/8
K:G
['A2 B cBA', 'A3 A2 a age dBd g3 gag', 'ABA g2 f ABA']  
X:1
L:1/8
M:6/8
K:G
|: A2 B cBA | eAB cBA | G3 EGG | DGG EGG | A2 B cBA | e2 d efg | age dBG | ABA A3 :: A2 a age | 
 dBd g3 | gag gfe | dBA G3 | EGG DGG | EGG ABc | Bed BAG | BAA A3 :: ABA g2 f | ABA gdB | 
 GAG e2 d | GAG edB | ABA g2 f | ABA efg | age dBG | ABA A3 :|  