Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:4/4
K:G
['G/G/G dG BAGB A/A/A', 'BcdB A/A/A']  
X:1
L:1/8
M:4/4
K:G
 d2 | G/G/G dG BAGB | A/A/A _FA _fAAd | G/G/G dG BAGB | A/A/A (fe/f/) gG G2 :: ef | gd ec BcdB | 
 A/A/A _FA _fA Ae/^f/ | gdec BcdB | A/A/A (Tfe/f/) gG G2 :|  