Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:9/8
K:G
['d2 A AGF']  
X:1
L:1/8
M:9/8
K:G
|: d2 A AGF AGF | d2 A AGF G3 | d2 A AGF AGF | GAB cAF G3 :|  