Craft a composition that integrates the assigned alphabet-related musical pattern and the provided melodic theme.
X:1
L:1/8
M:2/4
K:G
['D B2 AA GGFD GGB/A/G/A/ B2 z']  
X:1
L:1/8
M:2/4
K:G
 D | B2 AA | GGFD | GGB/A/G/A/ | B2 z D | B2 AA | GGFD | GGB/A/G/A/ | B2 z G/A/ | BBcB | BAAA | 
 GGAG | GFFE/F/ | GGAA | B2 cB | A4 | G2 z |]  