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:G
['G2 BG dGBG', 'G2 g2 edeg', 'GBDG BDGB', 'g2 fg']  
X:1
L:1/8
M:4/4
K:G
|: G2 BG dGBG | B2 BA BcBA | G2 BG dGBG | A2 AG AcBA | G2 BG dGBG | B2 BA B2 d2 | e3 f edef | 
 gedB A2 BA :: G2 g2 edeg | B2 BA BcBA | G2 g2 edeg | a3 b aged | G2 gf edeg | B2 BA B2 d2 | 
 e3 f edef | gedB A2 BA |: GBDG BDGB | DBBA BcBA | GBDG BDGB | ADFA DFAD | GBDG BDGB | DBBA B3 d | 
 e3 f edef | gedB A2 BA :: g2 fg efge | dBBA (3Bcd ef | g2 fg ef g2 | a3 b c'bag | g2 fg efge | 
 dBBA B3 d | e3 f edef | gedB A2 BA :|  