Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:Gdor
['gfdc Afdc', 'dgga gfdc']  
X:1
L:1/8
M:4/4
K:Gdor
|: fg | agfd gfdc | Afdc A2 GF | Acc/c/c Acfa | g3 a (3gag fd | agfa gfdc | Afdc d2 cA | 
 GFGA FGAc | dAcA G2 :: Ac | dgga gfdc | (3(A=Bc) de f2 gf | dcAG FDCA, | C/C/C A,C FAcf | 
 dgga gfdc | Afdc d2 cA | GFGA FGAc | dAcA G2 :|  