Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
M:6/8
K:D
['F2 D', 'f2 f dfd', 'FED d2']  
X:1
L:1/8
M:6/8
K:D
|: dAG F2 D | EGE F2 D | dAG F2 D | ECE GFE | dAG F2 D | EGE F2 D | GAB =cBA | GE=C EGE :: 
 f2 f dfd | afd ege | f2 f dfd | ged efg |1 f2 f dfd | afd ege | fed =cBA | GE=C EFG :|2 fed edc | 
 d=cB cBA | GAB =cBA | GE=C EGE :: FED d2 D | FED d2 D | FED d2 D | GEC EGE | FED d2 A | 
 e2 A f2 A | fed =cBA | GE=C EFG :|  