Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
Q:1/2=80
M:2/2
K:Bb
['B2 FB', 'f/g/4a/4 bfdf egce']  
X:1
L:1/8
Q:1/2=80
M:2/2
K:Bb
 d | B2 FB GBFB | EBDB Cccd | B2 FB Ggfe | dfce dBB :: f/g/4a/4 | bgdg egce | dfBd cFF f/g/4a/4 | 
 bfdf egce | dfce dBB f/g/4a/4 | bfdf egce | dfBd cFFf | g>fga bgfe | dfce dBB |]  