Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:3/8
K:D
['AFd d2 c BGe e2 d', 'FAd fda']  
X:1
L:1/8
M:3/8
K:D
 AFd | d2 c | BGe | e2 d | cAa | a2 g | f/g/a/g/ f/e/ | d2 A/B/ | AFd | d2 c | BGe | e2 d | dcB | 
 ABc | d/c/d/f/ e/c/ | d2 || f | gec | AGE | FAd | fda | ^g/a/b/a/g/f/ | e/d/c/B/ A/G/ | FAd | 
 fda | FAd | d2 c | BGe | e2 d | c/d/e/d/c/B/ | A/c/B/d/c/e/ | d/c/d/f/e/c/ | d2 :|  