Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
M:4/4
K:D
['Ad f3 g afef dedc B2', 'fg aAAA BAAA dedc B2']  
X:1
L:1/8
M:4/4
K:D
 Ad | f3 g afef | dedc B2 dc | BABc defa | e6 Ad | f3 g afef | dedc B2 g2 | fafd Acec | d6 :| fg | 
 aAAA BAAA | dedc B2 dc | BABc defa | e6 fg | aAAA BAAA | dedc B2 g2 | fafd Acec | d6 :|  