Develop a musical composition by integrating the alphabetically represented musical pattern and the supplied melodic theme.
X:1
L:1/8
Q:3/8=120
M:6/8
K:G
['GBe dBG', 'd g2 g gab']  
X:1
L:1/8
Q:3/8=120
M:6/8
K:G
 GBe dBG | B2 B B2 A | GBe dBG | A2 A A2 G | GBe dBG | g2 a b2 a | gfg e<ge | d2 B B2 d :: 
 g2 g gab | d2 d d2 d | g2 g gab | e2 e e2 d | def gfe | def gab | gfg e<ge | d2 B"^DC" B2 G |]  