Develop a musical composition based on the provided pattern of letters and incorporating the given motif within it.
X:1
L:1/8
Q:3/8=100
M:6/8
K:C
['g2 a gec', 'c3 dBG dBG egf edc agf edc']  
X:1
L:1/8
Q:3/8=100
M:6/8
K:C
 g2 a gec | afd gec | g2 a gec | dBG G3 | EGc Gce | fga def | efg GAB | c3 c3 :: dBG dBG | 
 egf edc | agf edc | Bdc BAG | cBc GA_B | A=Bc def | efg GAB | c3 c3 :|  