Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
Q:1/4=120
M:6/8
K:G
["B (dg).g (gf).g (abc') (bag) (dg)g (gf).g", "(d2 B) (dg)g gfg (abc') (bag) (gf).g", 'd G>AG B2', 'G2 d G>AG ABc def g2 g']  
X:1
L:1/8
Q:1/4=120
M:6/8
K:G
"^Playfully" B | (dg).g (gf).g | (abc') (bag) | (dg)g (gf).g | (afd) (d2 || B) | (dg)g gfg | 
 (abc') (bag) | (gf).g afd | (cB).A G2 |] | d | G>AG B2 B | cAe d2 d | G>AG B2 d | (cA).F G2 || d | 
 G>AG ABc | def g2 g | gbg afd | (cB)A G2 |]  