Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:2/2
K:D
['', 'A2 Ac dcde fefg abaf e^gaf ecAc', 'B2 [ca]2 [ca]4 [ca]2- [ca]2 AB cB']  
X:1
L:1/8
M:2/2
K:D
 z6 (3dcB |: A2 Ac dcde | fefg abaf | e^gaf ecAc | dfed BAFG | A2 Ac dcde | fefg abaf | 
 e^gaf ecAc |1 d2 de d2 (3dcB :|2 d2 de fg(3agf |: [_eb]2 [_eb]4 [_eb]2- | [eb]2 Bc dc B2 | 
 [ca]2 [ca]4 [ca]2- | [ca]2 AB cB A2 | [dg]2 [dg]4 gg | fefg abaf | e^gaf ecAc |1 d2 e2 fg(3agf :|2 
 d3 d d4 |]  