Develop a musical composition using the outlined alphabetical depiction of the structure and the provided theme.
X:1
L:1/8
Q:3/8=66
M:3/8
K:Bb
['FGA B2 c B/A/GF B3 GAB c2', 'F3 d2 c BAG c2 B AGF']  
X:1
L:1/8
Q:3/8=66
M:3/8
K:Bb
 FGA | B2 c | B/A/GF | B3 | GAB | c2 d | c/B/AG | F3 :| d2 c | BAG | c2 B | AGF | A2 G | FGA |1 
 Bc^c | d3 :|2 Bdc | B3 |]  