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
['a>aa a>gf', '[df]>[df][df] [df]>[df][df]']  
X:1
L:1/8
M:6/8
K:D
 a>aa a>gf | f>ff f>ff | b>bb b>ag | e>ee e2 z | a>aa a>gf | [df]>[df][df] [df]>[df][df] | 
 e>e[ce]/B/ [Ae]>Bc | [df]>[df][df] [df]2 z :: [df]>[df][df] [df]>[df][df] | 
 [df]>[df][df] [df]>[df][df] | e>e[ce]/B/ A>Bc | e>e[ce]/B/ A>Bc | [df]>[df][df] [df]>[df][df] | 
 [df]>[df][df] [df]>[df][df] | e>e[ce]/B/ A>Bc | [df]>[df][df] [df]2 z :|  