Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:4/4
K:G
['dBAB d2 Bd efge', 'bg ageg']  
X:1
L:1/8
M:4/4
K:G
|: G2 GA BAGB | dBeB dBAB | d2 Bd efge | dBAB GEDE | GFGA BAGB | d2 eB dBAB | d2 Bd efge | 
 dBAB G4 :: dggf g2 de | g2 bg ageg | eaag a2 eg | a2 bg ageg | dggf g2 de | g2 bg ageg | 
 d2 Bd efge | dBAB G4 :|  