Create a musical composition employing the given alphabetic structure and melodic theme.
X:1
L:1/8
M:4/4
K:G
['G2 BG cGBG', 'g2 dg']  
X:1
L:1/8
M:4/4
K:G
 F | G2 BG cGBG | ADDE FGAF | G2 BG cGBG | Addc AGG :| f | g2 dg Bgdg | g2 dg eaaf | g2 dg BgdB | 
 cAdc AGG :|  