Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:6/8
K:G
['F2 D D^CD', 'B3 cde dcB ABc']  
X:1
L:1/8
M:6/8
K:G
 F2 D D^CD | F2 D D^CD | F2 D D^CD | C2 C E3 | F2 D D^CD | F2 D D^CD | B3 cAF | AGF G2 A :: 
 B3 cde | dcB ABc | B2 G GAB | ABA A3 | B3 cde | dcB ABc | f2 f fed | cAF G3 :|  