Craft a musical work based on the specified structure and given theme.
X:1
L:1/4
M:4/4
K:G
['G A']  
X:1
L:1/4
M:4/4
K:G
 D | G D G A | B2 d2 | d/c/B/A/ G A | B2 z D | G D G A | B2 d2 | d/c/B/A/ G A | B2 z B | A G F G | 
 A2 B2 | B/A/ G A A | G2 z B | A G F G | A2 B2 | B/A/ G A A | G2 z |]  