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
['', '(B/A/) G>AG g>fg agf g2 (g/a/) b>ag', '', '(c/d/) ecA A>BA (e3 c2) c dBG', '', 'A>BA a3 f/f/ gdB cAF G3']  
X:1
L:1/8
M:6/8
K:G
"^A" |: (B/A/) | G>AG g>fg | agf g2 (g/a/) | b>ag efg | dec B2 :|"^B" || (c/d/) | ecA A>BA | 
 (e3 c2) c | dBG G>AG | (d3 B2) ||"^C" || (c/d/) | ecA A>BA | a3 !fermata!f2 f/f/ | gdB cAF | 
 G3 G2 |]  