Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/8
M:9/8
K:G
['D GAB c2 A', 'd gag fgf ege']  
X:1
L:1/8
M:9/8
K:G
 D | GAB c2 A Bcd | e2 c dBG F2 D | GAB c2 A cd=f | e2 c eBG G2 :: d | gag fgf ege | dge dBG A2 d | 
 gag fgf ege | d<ge dBG G2 d | gag fgf ege | dge dBG A2 d | GAB c2 A Bcd | e2 c dBG G2 :|  