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
['d2 B', 'def a3', 'def def dAF']  
X:1
L:1/8
M:6/8
K:D
|: d2 B cBA | dAF FED | d2 B cAA | dAF EFA | def Bcd | A3 F2 E | D3 DEF | AFE EFA :: dB/c/d fdf | 
 a3 afe | def a3 | bge edB | def a3 | bgb a2 g | fed dg/f/e | dAF EFA :: def def | dAF D3 | 
 def def | dAF EFA | def Bcd | A3 F2 E | D3 DEF | AFE EFA :|  