Compose a piece of music using the specified alphabetical notation system and the provided theme.
X:1
L:1/8
Q:1/2=100
M:4/4
K:Bb
['F2 B2 c2 d2 e2 f2 ed', 'de f2']  
X:1
L:1/8
Q:1/2=100
M:4/4
K:Bb
 F2 | B2 c2 d2 e2 | f2 ed c2 ef | gfed c3 B | B6 :: ga | baga baga | bagf gabf | gfed edcB | 
 c6 ef | g2 de f2 de | f2 ed c2 f2 | gfed c3 B | B6 :|  