Develop a musical composition by integrating the alphabetically represented musical pattern and the supplied melodic theme.
X:1
L:1/8
M:3/4
K:G
['F2 F2', 'F4 GABGAB c2 cBAG FGAFGA B2 BAGD']  
X:1
L:1/8
M:3/4
K:G
 B,2 B,4 | [BG]2 [BG]4 | gfedcB | A4 G2 | F2 F2 F2 | FG A4 | GBcBAG | G2 F4 :: GABGAB | c2 cBAG | 
 FGAFGA | B2 BAGD | B,2 B,4 | [BG]2 [BG]4 | (3cBA (3BGB, (3CB,A, | B,6 :|  