Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
M:3/4
K:Bb
['BGGF B>c d/c/B/c/ B2']  
X:1
L:1/8
M:3/4
K:Bb
 F>G BGGF | B>c d/c/B/c/ B2 | d>c BGGF | B>c d/c/B/c/ B2 | d2{e} dcdB | ed{d} cB G2 | B>c dcBG | 
 B>c BA/G/ FD | F4 d>c |{c} BA/G/{c} BA/G/{c} BA/G/ | B,C/D/ C>B, B2 ||  