Compose a piece of music following the given alphabetical representation of the musical structure and the provided motif.
X:1
L:1/4
M:4/2
K:G
['_B A']  
X:1
L:1/4
M:4/2
K:G
 G4 | _B2 B2 c2 c2 | d2 d c d3 c | _B2 c2 _e2 d d | c _B A B c3 c | d2 d2 c2 c2 | A4 =F4 | z4 =F4 | 
 _B2 B2 d2 d2 | c _B A B c3 d | _B A G2 G2 d2 | _B2 A2 G4 | z4 |]  