Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/8
Q:1/8=1
M:4/4
K:Amin
['A3 g g/f/ ee/_e/ cc/B/', 'e B3 g g/f/ ee/_e/ cc/B/ A', 'cA dA cA BA']  
X:1
L:1/8
Q:1/8=1
M:4/4
K:Amin
{^g}"Am" a2{^g} a{^g} a A3 g | g/f/ ee/_e/ cc/B/ A g2 | z a ^ga A3 g | g/f/ ee/_e/ cc/B/ A A2 :: 
 z"Am" e _ee"Em" B3 g |"Am" g/f/ ee/_e/ cc/B/ A e2 |"Am" z e _ee"Em" B3 g | 
"Am" g/f/ ee/_e/ cc/B/ A A2 ::[K:A]"A" z (3A/B/A/ GA BA cA | dA cA BA e2 | z (3A/B/A/ GA BA cA | 
 dA cA BA A2 :|  