Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/4
M:3/2
K:G
['G G']  
X:1
L:1/4
M:3/2
K:G
 z4 G G | B3 G/G/ A B | G3- G G d | d3 d/d/ =f e | d3- d d g | d3 B/B/ d B | G2 d d e G | 
 B3 G A B | G3 z2 z |]  