Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:6/8
K:D
['d2 d cBA B2 B AGF', 'd f2 e def e2 d cde']  
X:1
L:1/8
M:6/8
K:D
 A | d2 d cBA | B2 B AGF | GAG FED | EFG ABc | d2 d cBA | B2 B AGF | EFG ABc | (d3 d2) :: d | 
 f2 e def | e2 d cde | D2 c Bcd | c2 B A2 d | f2 e def | e2 d cde | dcB e2 ^G | (A3 A2) :|  