Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
M:4/4
K:G
['(3cBA GB,DG BDGB dGBd gbag fedB =cAFA', 'G2 (3bbb bB^df bagf e^def gfg^g aA^ce']  
X:1
L:1/8
M:4/4
K:G
|: (3cBA | GB,DG BDGB | dGBd gbag | fedB =cAFA | GBAG (3FED (3cBA | GB,DG BDGB | dGBd gbag | 
 fedB =cAFA | G2 GF G2 :: (3bbb | bB^df bagf | e^def gfg^g | aA^ce agfe | (3ded ^ce d2 ab | 
 c'afd ^cdef | gfga b2 ag | fedB =cAFA | G2 GF G2 :|  