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
['B2 GGFG']  
X:1
L:1/8
M:6/8
K:G
 B2 GGFG | B2 GGFG | A2 AABc | e2 d d2 B | B2 GGFG | B2 GGFG | ABcDEF | A3 G2 z |]  