Craft a piece of music that integrates both the suggested theme and letter-based structure.
X:1
L:1/8
Q:1/8=180
M:6/8
K:G
['def gag fed']  
X:1
L:1/8
Q:1/8=180
M:6/8
K:G
 DGG BAB | cAG FGA | DGG BAB | cAF G2 G | DGG BAB | cAG FGA | fed f2 d | cAF G2 z | DGG BAB | 
 cAG FGA | DGG BAB | cAF G2 G | DGG BAB | cAG FGA | fed f2 d | cAF G2 z | def gag | fed g2 B | 
 def gag | fed cAF | def gag | fed g2 d | fed f2 d | cAF G2 z | def gag | fed g2 B | def gag | 
 fed cAF | def gag | fed g2 d | fed f2 d | cAF G2 z ||  