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
['F2 E2', 'E2 FEFG A2 AB c2 c2 (3BcB']  
X:1
L:1/8
M:2/2
K:A
 B2 |"A" c4 cBAB | cBAG F2 E2 | c4 cBAB | cBce"D" f2 e2 |"A" c4 cBAB | cBAG F2 E2 | c4 cB A2 | 
"F#m" F3 E F2 :: E2 |"D" F3 E F2 E2 | FEFG A2 E2 | FEFG A2 AB |"A" c2 c2 (3BcB A2 |"D" F3 E F2 E2 | 
 FEFG A2 AB |"A" c2 c2 (3BcB A2 |"F#m" F3 E F2 :|  