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
['GFG DED', 'BAB dBG', 'd efg efg dBG GBd']  
X:1
L:1/8
M:6/8
K:G
 d | edB GFG | DED GFG | DED cBA | BGE E2 d | edB GFG | DED GAB | AGF GBA | GFE D2 :| d | BAB dBG | 
 BAB dBG | ABA AGA | BGE E2 D | BAB deg | age d2 B | cBA GBA | GFE D2 :| d | efg efg | dBG GBd | 
 eaa aga | bge e2 |1 d | efg efg | dBG GBd | gfe dgb | agf e2 :|2 e | def gba | gfe d2 B | 
 cBA GBA | GFE D2 |]  