Construct a music composition that complies with the designated structure and theme.
X:1
L:1/8
M:2/4
K:Bb
['B>GBB/G/ FBGB/G/ F>D F2']  
X:1
L:1/8
M:2/4
K:Bb
 BB/B/cc/c/ | B>GBB/G/ | FBGB/G/ | F>D F2 | FB/B/GB/G/ | G/B/B/D<FF/ | FBGB/G/ | FF F2 | 
 BB/G/BB/G/ | B>GBB/G/ | FBGB/G/ | F>D F2 | FB/B/GB | G/B/B/D/F z | FBGB/G/ | FF F2 |]  