Construct a melodic piece using the designated alphabetic pattern and the provided musical theme.
X:1
L:1/8
M:6/8
K:Bb
['F>GA B>cd', '(F<BB) (G<BB)']  
X:1
L:1/8
M:6/8
K:Bb
 F | F>GA B>cd | e>dc dcB | (A<ff) (B<gg) | (B<bb) (B<ff) | F>GA B>cd | cde fga | bge dec | 
{d} cBB B2 :: A | (F<BB) (G<BB) | (F<BB) (G<BB) | FB/B/B Bcd | e2 d c2 B | FB/B/B GB/B/B | 
 FB/B/B GB/B/B | bge dec |{d} cBB B2 :|  