Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/4
M:4/4
K:G
['D D']  
X:1
L:1/4
M:4/4
K:G
 D D D D | D B G2 | D c A2 | d d B2 | D D D D | D B G2 | A G F/F/E/E/ | D3 z | D c c2 | B G G2 | 
 A F E/E/F/F/ | G B d2 | D c c2 | B G G2 | A F E/E/F/F/ | G3 z |]  