Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:2/4
K:G
['FG AB c2', 'FA- AG', 'AG DG- G2 FA- AG FG Ac']  
X:1
L:1/8
M:2/4
K:G
|: FG AB | c2 Bc | dA- AG | FD- D2 | FG AB | c2 BG |[M:3/4] FA G2 G2 ::[M:2/4] Bd- de | fg fe | 
[M:3/4] dB FA- AG |[M:2/4] FG A2 | Bd- de | fg fe | dB FG | AF D2 :: FA- AG | FG Ac | BG AG | 
 DG- G2 | FA- AG | FG Ac | BG AG | D2 D2 :|  