Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:4/4
K:D
['BE E2', 'f2 fe']  
X:1
L:1/8
M:4/4
K:D
 dc | BE E2 BEdE | BE E2 BcdB | cA A2 cdeA | cdef e2 :| ge | f2 fe dcBA | fgfe d3 e | f2 fe fgaf | 
 ecAc e2 :|  