Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:G
['', 'AGGF G2', 'AGGF G2']  
X:1
L:1/8
M:4/4
K:G
 dc |: B2 cA BdcA | BdcA B2 AG | d2 ec d2 ec | dfec dcBA | e2 fd edcB | Add^c d=cBA | BGcA B2 AG | 
 FGAB cBcA | G2 ge fdcA | FGAB cAFG | AGGF G2 FG |1 AGGF G2 dc :|2 AGGF G2 GF |: G2 =f2 e2 f2 | 
 G2 =fg fdcA | G2 g2 ^f2 g2 | d2 ga gfdc | A2 =f2 e2 f2 | d^cde ^fd (3efg | af ge fd ed | 
 (3ddd egfd cA | G2 ge fdcA | FGAB cAFG | AGGF G2 FG |1 AGGF G2 GF :|2 AGGF G4 ||  