Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:6/8
K:G
['G2 A', 'e2 f g3']  
X:1
L:1/8
M:6/8
K:G
|: edB G2 A | Bed Bcd | edB G2 A | BAF GFE | DB,D G2 A | Bed Bcd | edB gdB | BAG ABd :: e2 f g3 | 
 eag fed | e2 f g3 | efg a3 | bag agf | gfe def | g3 fdB | BAG ABd :|  