Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:A
['', 'efed cAcd efae fecd efed cBAc', 'FEDF EDEF D2']  
X:1
L:1/8
M:4/4
K:A
 cd |: efed cAcd | efae fecd | efed cBAc | BABc ABcd | efed cAcd | efae fecd | efed cBAc |1 
 BABc A2 cd :|2 BABc A2 A2 |:[K:D] ABAG FDFG | ABAG FDFG | ABAG FEDF | EDEF D2 FG | ABAG FDFG | 
 ABAG FEDF | EDEF D2 e2 | efed cBAc | BABc A2 cd :|  