Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:2/2
K:Bb
['B2 FB', 'bfdf egce']  
X:1
L:1/8
M:2/2
K:Bb
 d | B2 FB GBFB | EBDB C (c2 d) | B2 FB Ggfe | dfcf dBB :| (3f/g/a/ | bfdf egce | 
 dfBd cFF (3f/g/a/ | bfdf egce | Bgfc dB B(3f/g/a/ | bfdf egce | dfBd cFFf | gfga bgfe | 
 dfcf dBB ||  