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:D
['DFA d2 e fdB BAF', 'def afd']  
X:1
L:1/8
M:6/8
K:D
 DFA d2 e | fdB BAF | ABA AFD | EFE GFE | DFA d2 e | fdB BAF | AFA dzF | DED D2 A :| def afd | 
 g2 b afe | def afd | cee ecA | dfa afd | gbg faf | BdB AFA | DED D2 A :|  