Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:6/8
K:Bb
['D{E}FF F2 d']  
X:1
L:1/8
M:6/8
K:Bb
 E |"Bb" D{E}FF F2 d |"F" c>Bc"Gm" dBG |"Bb" D{E}FF F2 d |"F" c3{Bcd} G2 z |"Bb" D{E}FF F2 d | 
"F" c>Bc"Gm" dBG |"Eb" g{a}bg"Bb" fdb |"F" fdB"Bb" B2 :| g |"Bb" fdf bf_a |"Eb" geg"Bb" fdB | 
"Bb" fdf bf_a |"Eb" g>fg"F7" c2 g |"Bb" fdf bf_a |"Eb" geg"Bb" fdB |1"Eb" g>ab"Bb" fdB | 
"F7" FBA"Bb" B2 :|2"Cm" gec"Bb" fdB |"F7" FBA"Bb" B2 |]  