Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:4/4
K:G
['B>c d>BG>B c>AF>A (3GFG A>F G>AB>c d>gf>g', 'G2 B>c d>gf>g e>gf>g d>g (3gfg e>gf>g']  
X:1
L:1/8
M:4/4
K:G
 B>c | d>BG>B c>AF>A | (3GFG A>F G>AB>c | d>gf>g e>fg>e | d>BG>B A2 B>c | d>BG>B c>AF>A | 
 (3GFG A>F G>AB>c | d>gf>g e>cA>F | G2 B2 G2 :: B>c | d>gf>g e>gf>g | d>g (3gfg e>gf>g | 
 d>gf>g e>fg>e | d>BG>B A2 B>c | d>BG>B c>AF>A | G>DB,>D G>AB>c | d>gf>g e>cA>F | G2 B2 G2 :|  