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
['AD (3FED']  
X:1
L:1/8
M:4/4
K:D
|:"Em" Beed BcdB |"D" AD (3FED AD (3FED |"Em" E3 F GFGA |1 Beef gfed :|2 Beed e2 ef |: gfga bgeg | 
"D" fefg afdf |1"Em" gfga bgeg |"^B or D" fefg"Em" e3 f :|2"Em" g2 bg"D" f2 af | edef"Em" g4 ||  