Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:2/2
K:G
['efgf edBd ceAc BdGB', 'gfga bgdg']  
X:1
L:1/8
M:2/2
K:G
 D2 | (3.G.G.G BG d2 BG | efgf edBd | ceAc BdGB | ABcA GFED | (3.G.G.G BG d2 Bd | efgf edBd | 
 ceAc BdGB | cAFA G2 :: d2 | gfga bgdg | edef gdBd | gfga bgdg | edcB A2 (Bd) | gfga bgdg | 
 edef gdBG | DGBd gdBd | cAFA G2 :|  