Develop a musical composition by integrating the alphabetically represented musical pattern and the supplied melodic theme.
X:1
L:1/8
M:2/4
K:Bb
['f2 (fd) B2 (BF) D2 (DF) B2', 'z2 defg f2 (bf) d2 (fd) B2']  
X:1
L:1/8
M:2/4
K:Bb
 f2 (fd) | B2 (BF) | D2 (DF) | B2 (Bd) | f2 (fe) | c2 (cB) | (Ac) (FA) | B2 z2 :| defg | f2 (bf) | 
 d2 (fd) B2 (dB) | ABcd | c2 (ec) | (Ac) (FA) | B2 z2 :|  