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=160
M:6/8
K:G
['eAA fAA gfg age', 'efg a2 a aba age']  
X:1
L:1/8
Q:1/8=160
M:6/8
K:G
"^A dorian" gf | eAA fAA | gfg age | dBG GFG | BAG Bcd | eAA fAA | gfg age | dBd gdB | ABA A :| 
 z d | efg a2 a | aba age | def g2 g | gba ged | efg a2 a | aba age | dBB gBB | ABA A :|  