Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
Q:1/8=160
M:6/8
K:G
['cAG FGA', 'G2 B/c/ ded dcB cdc cBc ded']  
X:1
L:1/8
Q:1/8=160
M:6/8
K:G
 D | DGA B2 d | cAG FGA | BdB AFD | GBG AFD | DGA Bcd | cAG FGA | B/c/dB AFD | DGG G2 :| B/c/ | 
 ded dcB | cdc cBc | ded =fef | dgg g2 a | bag =fed | cAG FGA | B/c/dB AFD | DGG G2 :|  