Utilizing the provided musical theme and letter-based structure, compose a piece of music.
X:1
L:1/4
M:2/4
K:G
['b2 a g f e d z', 'z b d g B c e']  
X:1
L:1/4
M:2/4
K:G
 b2 a g | f e d z | e2 d c | B A G z | b2 a g | f e d z | e c Tf e/f/ | g z [gB] z |: b d g B | 
 c e A2 | e A c F | G B D2 | B ^G d2- | d ^c A2- | A D =c2- | c B G2 :|  