Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/8
M:9/8
K:G
['FGA BGB', 'cAG FGA']  
X:1
L:1/8
M:9/8
K:G
 DGG GAG FGA | BGB cAB c2 c | DGG GAG FGA | BGB cAF G2 G/F/ | DGG GAG FGA | BGB cAB c2 B/c/ | 
 ded cAG FGA | BGB cAF G2 || B/c/ | ded cAG FGA | ded cAB c2 B/c/ | ded cAG FGA | BGB cAF G2 B/c/ | 
 ded cAG FGA | ded cAB c2 d/e/ | fed cAG FGA | BdB cAF G2 ||  