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
['FAF DFA', 'add bdd add fed cec ABc']  
X:1
L:1/8
M:6/8
K:D
|: AG | FAF DFA | GBG E2 d | cec ABc | dcB A2 G | FAF DFA | G/A/BG E2 d | c/d/ec ABc | dce d :: 
 fg | add bdd | add fed | cec ABc | dfb afg | add bdd | add fed | cec ABc | dce d :|  