Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:2/2
K:A
['ecdB AGBG FEFG', 'A2 cAce ecBA dBdf fdcB cAce fdfa', "abc'b afaf", 'ECFD GEAF']  
X:1
L:1/8
M:2/2
K:A
|: ecdB AGBG | FEFG Acef | ecdB AGBG | FEFG A2 A2 :: cAce ecBA | dBdf fdcB | cAce fdfa | 
 gegb a2 a2 :: abc'b afaf | ecec BABc | abc'b afaf | ecdB A2 A2 :: ECFD GEAF | Acec BABc | 
 ECFD GEAF | dBAG A2 A2 :|  