Craft a composition that integrates the assigned alphabet-related musical pattern and the provided melodic theme.
X:1
L:1/4
M:3/4
K:G
['F G']  
X:1
L:1/4
M:3/4
K:G
 D/D/ | G3/2 F/ G | A e d/d/ | c E F | G e d | B F G | A e d/d/ | c E F | G z |]  