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
['G3 A B2', 'G2 (Bc) (dc)de =f2 ef dggf g2']  
X:1
L:1/8
M:4/4
K:G
 D2 | G3 A B2 AG | F>GAB c2 Bc | d>e=fe dcA^F | G3 F D2 (3(DEF) | G3 A B2 (AG) | F>GAB c2 Bc | 
 d>e=fd cA^FA | G4 G2 || | (Bc) | (dc)de =f2 ef | dggf g2 de | =f2 ag fedB |{d} cBAG F2 (3(DEF) | 
 G3 A B2 (AG) | F>GAB c2 Bc | d>e=fd cA^FA | G4 G2 |]  