Develop a musical composition by integrating the alphabetically represented musical pattern and the supplied melodic theme.
X:1
L:1/4
M:4/4
K:G
['G G']  
X:1
L:1/4
M:4/4
K:G
 D | G G G d | B/A/ G A A/B/ | c c c d | B B B d | A A A d/c/ | B2 A2 | G2 z |]  