Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:6/8
K:G
['cAF G2', 'BAG A2 a aga bge edB def']  
X:1
L:1/8
M:6/8
K:G
 BGG dGG | cAG FGA | BAG BdB | cAF G2 A | BGG dGG | cAG FGA | def gdB |1 cAF G2 A :|2 cAF G2 B |: 
 def g3 | edc BAG | A2 a aga | bge edB | def gfg | edc BAB | GB/c/d gdB |1 cAF G2 B :|2 cAF G3 ||  