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
['FDFA d3 A']  
X:1
L:1/8
M:4/4
K:D
|: E2 CE A,ECE | FDFA d3 A | B2 dB A F3 | BAGF EDCD | E C3 A,CEG | FDFA d3 A | BdcB A F3 | 
 EDCE D3 D :|  