Compose a piece of music by integrating the assigned letter representation and provided tune.
X:1
L:1/4
M:4/2
K:G
['B4 A4']  
X:1
L:1/4
M:4/2
K:G
 G8 | B4 A4 | B4 c4 | d4 z2 e2 | d4 B4 | G8 | G8 | B4 A4 | B4 c4 | d4 z2 e2 | d4 B4 | G4 d4 | 
 B4 A4 | G4 D4 | A2 B2 c2 B2 | G8 |]  