Develop a musical piece incorporating the designated alphabet-based pattern and the supplied melodic theme.
X:1
L:1/4
M:2/2
K:F
['B A G']  
X:1
L:1/4
M:2/2
K:F
|: C |"F" F2 A G/F/ |"C7" G3 B |"F" A2"C7" G2 |"F" F/E/F/G/"^(C7)" F G |"F" A F C A |"C" G3 F | 
"C" E c"G7" D =B |"C" c3 :: A/B/ |"F" c2"Bb" d3/2 c/ |"C7" B A G c |"^(Bb)" B A G F |"C7" E G C2 | 
"F" F E/F/"C7" G F/G/ |"F" A G/A/"Bb" B c/B/ |"F" A G/F/"C7" C E |"F" F3 :|  