Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
M:2/2
K:G
['AG G2', 'dg g2', 'AG G2', 'dg g2']  
X:1
L:1/8
M:2/2
K:G
 AG G2 AGFD | AG G2 Addc | AG G2 AGFD | FEFG ABcA :| dg g2 aggf | dgge fdcA | dg g2 aggf | 
 d^cde fd=cA | dg g2 ag (3efg | a3 g f3 g | afge fde^c | d2 eg fdcA ||"^Variations:" G3 B AGFD | 
 AG G2 AdcA | AGGB AGFD | F3 G AdcB | AG G2 AD D2 | AG G2 ABcA | G3 B AGFD | FEFG ABcA || 
 dg g2 ag g2 | dg g2 fdcA | dg g2 ag g2 | d2 eg fdcA | dg g2 bg g2 | abag fefg | 
 af (3gfe fd (3efe | dfeg fdcA ||  