Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:4/4
K:C
['BADA dAFA', 'dfaf bgaf']  
X:1
L:1/8
M:4/4
K:C
[M:2/2][K:D] .abc B | BADA dAFA | BADA defd | BADA dAFA ||1 dcdf e2 d :|2 dbaf e2 d || d | 
 dfaf bgaf | dfaf (3gag fe | dfaf bgaf | dBAf e2 dd | dfaf bgaf | bgaf g2 fg | agfe dBAB | 
 dbaf e2 d | |]  