Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
Q:1/8=180
M:6/8
K:G
['G2 G B/c/dB GBG B2 A GBG', 'A g3 def gfe', 'BGG ADD', 'gdB gdB']  
X:1
L:1/8
Q:1/8=180
M:6/8
K:G
|: G2 G B/c/dB | GBG B2 A | GBG GB/c/d/B/ | A=FA c2 A | G3 GB/c/d/B/ | GAB gdB | cac BgB | 
 A=FA c2 A :: g3 def | gfe dBG | g3 de=f | A=FA c2 A | g3 def | gfe dcB | cac BgB | A=FA c2 A :: 
 BGG ADD | BGG ABc | BGG ADD | A=FA ABc | BGG ADD | GAB gdB | cac BgB | A=FA c2 A :: gdB gdB | 
 GAB d2 B | gdB gdB | A=FA c2 A | gdB gdB | GAB gdB | cac BgB | A=FA c2 A :|  