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:G
['BAG AGE GBd g3 ded BGA', 'aga bge dBG']  
X:1
L:1/8
M:6/8
K:G
 BAG AGE | GBd g3 | ded BGA | BAA Adc | BAG AGE | GBd g3 | ded BGA |1 BGG Gdc :|2 BGG GBc || 
 dgg ged | eaa aga | bge dBG | BAG ABc | dgg ged | eaa aga | bge dBG | AGE GBc | dgg ged | 
 eaa aga | bge dBG | BAG Adc | BAG AGE | GBd g3 | ded BGA | BGG Gdc :|  