Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
Q:1/8=128
M:4/4
K:Gmin
['B<G G>F D<a']  
X:1
L:1/8
Q:1/8=128
M:4/4
K:Gmin
|: F | D<G G>F D<G G>A | F>G A>B c/B/A/G/ F>A | B<G G>F D<a f>=e | f>c d/c/B/A/ B<G G2 | 
 D<G G>F D<G G>A | F>G A>B c/B/A/G/ F>A | B<G G>F D<a f>=e | f>c d/c/B/A/ B<G Gf | 
 g>a b<g d>g b>g | a/g/f/d/ c>=e f>c a<f | g>a b<g d>g b>g | b/a/g/=e/ d<a g/g/g g2 | 
 d>g b>g a>f g<d | f>c A>f c/B/A/G/ F>d | B<G G>F D<a g>e | f>c d/c/B/A/ B<G G :|  