Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/8
Q:1/8=120
M:2/4
K:G
['g2 dB', '', 'B2 dB c2']  
X:1
L:1/8
Q:1/8=120
M:2/4
K:G
 G | B2 dB | c2 ec | Bd Bd | AF ED |"^5" g2 dB | g2 dB | cA FD | G2 G :| z |:"^9" G2 BG | G2 BG | 
 A2 cA | A2 cA |1"^13" B2 dB | c2 ed | cB AG | FA FD :|2"^17" B2 dB | c2 ec | BG AF | 
 !fermata!G4 |]  