Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:4/4
K:C
['BA G4-']  
X:1
L:1/8
M:4/4
K:C
 GG | G G2 G G2 EE | GA GF E2 GG | Ac cA c c2 A | cd cA G2 BA | G4- GE FE | C6 GG | GG GG G2 EE | 
 GA GF E2 G-G | Ac cA c c2 A | cd cA GG BA | G4- GE FE | C6 GG | A4 Ac ed | c2 G4 BA | G4- GG AG | 
 E6 GG | A4 Ac ed | c2 G4 GA | B4- Bd AB | c6 |]  