Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/4
Q:1/4=200
M:2/2
K:D
['a f d f a g e', 'd e']  
X:1
L:1/4
Q:1/4=200
M:2/2
K:D
 a | f d f a | g e f3/2 e/ | d e f e | d c A2 | A A A/B/A/F/ | G G A/B/c/A/ | d2 c/d/e/c/ | d2 d :| 
 A | d e f g | a f g f/g/ | a b g a | f d e a | a f g e | f d e3/2 c/ | d e f e | d c A a | 
 a b g a | f d e3/2 c/ | d e f e | d c A2 | A A A/B/A/F/ | G G A/B/c/A/ | d2 c/d/e/c/ | d2 d |]  