Develop a musical composition by integrating the alphabetically represented musical pattern and the supplied melodic theme.
X:1
L:1/8
M:12/8
K:G
['DED G2 A B2 G', 'B2 G']  
X:1
L:1/8
M:12/8
K:G
 DED G2 A B2 G cAG | F2 D DED F2 D DED | DED G2 A B2 G ABc | ded cAF G3- G3 :: B2 G c2 A B2 G cAG | 
 F2 D DED F2 D DED | B2 G c2 A d2 B ABc | ded cAF G3- G2 z :|  