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:A
['a2 gf eAcA', 'eABc dfeA Bcdf', 'ga eABc dfeA Bcdf e2 (3efg a2']  
X:1
L:1/8
M:4/4
K:A
|: a2 gf eAcA | defd e2 (3efg | a2 gf eAcA | dBcA B2 (3efg | a2 gf eAcA | defd e2 (3efg | 
 a2 AA/A/A eAcA |1 B2 AB cA A2 :|2 B2 AB cAdc |: BEE/E/E BcdB | cFF/F/F A3 B | ADED ADFA | 
 dcdf edcd | BEE/E/E BcdB | cFF/F/F A3 f/g/ | a2 gf eAcA |1 B2 AB cAdc :|2 B2 AB cA A2 |: 
 eABc dfeA | Bcdf eABc | dfeA Bcdf | e2 (3efg a2 ga | eABc dfeA | Bcdf e2 (3efg | a2 gf eAcA | 
 B2 AB cA A2 :|  