Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:6/8
K:Bmin
['d2 B', 'dBB B2']  
X:1
L:1/8
M:6/8
K:Bmin
|: d2 B BAB | F2 B BAB | d2 B Bcd | cBc ABc | d3 e3 | f2 b afe | dcB AFE |1 FBB B2 c :|2 
 FBB B2 ^g |: a3 f3 | e3 cBA | c2 A cBA | cde f2 e | d2 B BAB | F2 B Bcd | efg fef |1 dBB B2 ^g :|2 
 dBB B2 c ||  