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
['B2 dB ceec BddB ABGA BddB cdef', 'gabg eaaf']  
X:1
L:1/8
M:4/4
K:G
 B2 dB ceec | BddB ABGA | BddB cdef | gabg a2 gd :| gabg eaaf | gabg e2 d2 | gabg eaaf | 
 gedB A2 G2 :|  