Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
Q:1/4=120
M:7/8
K:D
['b2 b2 a2 g']  
X:1
L:1/8
Q:1/4=120
M:7/8
K:D
|:"D" a2 a b2 b2 | a2 g f^e fg | a a2 b2 b2 | a2 g f2- f2 :|  