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
['AFD EDB, DFA', 'ecA dcd']  
X:1
L:1/8
M:6/8
K:D
 A | FDA, DFB | AFD EDB, | DFA def | g3 eag | fdB AFD | EDB, DFA | d3 eag | fdc d3 :| afa geg | 
 fdf ecA | dcd fed | cAc efg | afa g2 a | egf ecA | dcd eag | edc d3 :|  