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:Bmin
['fbb fga efd', 'fBc d2 e', 'fBc d2', 'fba fBc d2 f fed cBc Ace']  
X:1
L:1/8
M:6/8
K:Bmin
 fbb fga | efd cBA | d3 ede | f2 e f=ga | fbb fga | efd cBc | Ace aec |1 B3 B2 e :|2 B3 B2 =g |: 
 fBc d2 e | fed cBA | fBc d2 e | f2 e fba | fBc d2 e | fed cBc | Ace aec |1 B3 B2 =g :|2 B3 B2 e || 
 fbb faf | fed cBA | d3 ede | f2 e fba | fbb faf | fed cBc | Ace aec | B3 Bde :: fBc d2 f | 
 fed cBA | fBc d2 e | f2 e fba | fBc d2 f | fed cBc | Ace aec | B3 Bde :|  