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=100
M:6/8
K:Dmix
['fdd dc/d/A ddc/d/ e2 A fdf fe/f/d', 'a3 eee cB/c/A fe/f/d g2 a bag']  
X:1
L:1/8
Q:1/8=100
M:6/8
K:Dmix
 fdd dc/d/A | ddc/d/ e2 A | fdf fe/f/d | fgf/g/ a3 || eee cB/c/A | fe/f/d g2 a | bag a3/2 g/f/e/ | 
 fed/e/ d3 ||  