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:G
['GB B/c/B/A/', 'g2 g>f', 'B2 B>c dB']  
X:1
L:1/8
M:2/4
K:G
 GB B/c/B/A/ | GB B/c/B/A/ | FA D>A | FA D>A | GB B/c/B/A/ | GB g>e | fd cA | G2 G2 :| g2 g>f | 
 ga ag | fd dd/e/ | fg af | g2 g>f | gb ag | fd cA | G2 G2 :| B2 B>c | dB AG | F>E FG | AB c/B/A | 
 B2 B>c | dB Bg | fd cA | G2 G2 :|  