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 B', 'A dBG AFD dBG (Af).f e2 e']  
X:1
L:1/8
M:6/8
K:D
 AS | d2 d def |{ef} g2 e c2 A | d2 B A2 F | d2 B AFD | d2 d def |{ef} g2 e c2 A | d2 B A2 F | 
 TE>DE D2 || d | e2 e efg |{fg} a2 f d2 A | dBG AFD | dBG (Af).f | e2 e efg |{fg} a2 f d2 B | 
 cBA TG>FE | A3- ABc!D.C.!S |]  