Create a composition by utilizing the given alphabet-based musical pattern and the provided melodic theme.
X:1
L:1/8
M:4/4
K:G
['Gedc B3 A Ggfe d3 d ecBA']  
X:1
L:1/8
M:4/4
K:G
 Gedc B3 A | Ggfe d3 d | ecBA dBAG | ecdB A4 |:  