Craft a composition that integrates the assigned alphabet-related musical pattern and the provided melodic theme.
X:1
L:1/8
M:2/4
K:Bb
['FFBA GG c2 A>GFF B2 z']  
X:1
L:1/8
M:2/4
K:Bb
 FFBA | GG c2 | A>GFF | B2 z F | FFBA | GG c2 | A>GFF | B2 z c/c/ | ccff | d>cBB | dc B2 | FFBA | 
 GGcc | d>dcc | B4 |]  