Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:Emin
['BE GA B>c BG', 'eB Bd/e/ f/{g}f/ e']  
X:1
L:1/8
M:4/4
K:Emin
 B/c/ | BE GA B>c BG | A>B AF BE GB/c/ | BE GA B>c BG | AF BF E2 E :: (3B/c/d/ | 
 eB Bd/e/ f/{g}f/ e d>B | d>e d B/{c}B/ A FA B/d/ | eB Bd/e/ f/{g}f/ e dB | d B/{c}B/ AF E2 E :|  