Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
Q:1/2=90
M:4/4
K:G
['DGBG dGBG DGBG EA A2 DGBG dBeg', 'dgbg agbg']  
X:1
L:1/8
Q:1/2=90
M:4/4
K:G
 DGBG dGBG | DGBG EA A2 | DGBG dBeg | dcBA G>G G2 :| d>g g2 dgbg | agbg ea a2 | dg g2 dgbg | 
 agbg eg g2 | d/g/ g3 dgbg | agbg ea a2 | g<be<a d<gB<g | dcBA G<G G2 |]  