Create a composition by utilizing the given alphabet-based musical pattern and the provided melodic theme.
X:1
L:1/8
M:4/8
K:D
['A G F']  
X:1
L:1/8
M:4/8
K:D
 D E F G | A G F E | D2 D2 | D4 | D E F G | A G F E | D2 D2 | D4 | E E E E | F4 | G G G G | A4 | 
 B c d c | B A G F | E2 E2 | D4 |]  