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=160
M:6/8
K:D
['FEF FED fed =cAG', 'gfe ceA']  
X:1
L:1/8
Q:1/8=160
M:6/8
K:D
 z | FEF FED | fed =cAG | EGE =CEG | =ced cAG | FEF FED | fed =cAG | E=CE =cBA | FGE D2 :| e | 
 gfe ceA | ceA ceA | gfe ceA | cAc d2 e | gfe ceA | cAA BAG | EFE =cBA | FGE D2 :|  