Develop a musical composition by integrating the alphabetically represented musical pattern and the supplied melodic theme.
X:1
L:1/8
M:12/8
K:A
['c2 B', 'c2 B']  
X:1
L:1/8
M:12/8
K:A
|: e2 A c2 B A2 c BAB | c2 B Bcd f2 e c2 e | e2 A c2 B A2 c BAB | cec B2 c A3 A3 :: 
 c2 B Bce f2 e c2 B | c2 B Bce f2 e c2 d | e2 a c2 B A2 c BAB | cec B2 c A3 A3 :|  