Develop a musical composition using the outlined alphabetical depiction of the structure and the provided theme.
X:1
L:1/8
M:6/8
K:G
['dBB B2 A', 'g2 g aga bge']  
X:1
L:1/8
M:6/8
K:G
|: dBB BAB | dBB Bge | dBB B2 A | GEE Ege | dBB BAB | dBd g2 e | dBB B2 A | GEE E3 :: g2 g aga | 
 bge dBd | g2 g aga | bge ega | bag age | ged g2 e | dBG AGE | GED D3 :|  