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:Bmin
['AB BA', 'gf d2 ea gf ed e2 fg']  
X:1
L:1/8
M:2/4
K:Bmin
|:"Bm"{c} AB BA | BA d{f}d | AB BA | BA{f} d2 | AB BA | Bc de |"A" cd{e} c{B}A |"Bm"{f} Bc B2 :: 
"Em" z e2 e |{b} ed e2 | e>f gf | e2"D" d2 |"A" ea gf |"Em"{b} ed e2 |1"D" fg f/e/d |"Em" e3 z :|  