Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:3/8
K:C
['g2 e/f/', 'g a/g/fe']  
X:1
L:1/8
M:3/8
K:C
 g2 e/f/ | g2 e/f/ | gfe | d3 | def | gag | fed |1 e2 c :|2 c2 c |: d/e/fg | d2 g | a/g/fe | dec | 
 d/e/fg | d2 g | a/g/fe |1 d2 c :|2 d2 G ||  