Craft a piece of music that integrates both the suggested theme and letter-based structure.
X:1
L:1/8
M:12/8
K:D
['gbg dgd BdB GBG FAF DEF']  
X:1
L:1/8
M:12/8
K:D
|: gbg dgd | BdB GBG | FAF DEF | GA_B =Bde | gbg dgd | BdB GBG | FAF DEF | G3 G3 :|  