Create a composition by utilizing the given alphabet-based musical pattern and the provided melodic theme.
X:1
L:1/8
M:6/8
K:Bb
['D2 E F2 B BAG G2 F']  
X:1
L:1/8
M:6/8
K:Bb
 D2 E F2 B | BAG G2 F | CEGFAc | B4- B z | D2 E F2 B | BAG G2 F | CEGFAc | B4- BF | F2 ddcc | 
 BddcBA | GGGAGA | B4- BF | F2 ddcc | BddcBA | GGGAGA | B4- B z |]  