Craft a piece of music that integrates both the suggested theme and letter-based structure.
X:1
L:1/8
Q:1/2=60
M:2/2
K:G
['GA B2 B2 c2 BA Bdef g2', 'g2 fg']  
X:1
L:1/8
Q:1/2=60
M:2/2
K:G
 GA | B2 B2 c2 BA | Bdef g2 fg | dcAG GABc | d6 GA | B2 B2 c2 BA | Bdef g2 fg | efde BdAB | G6 :: 
 G2 | g2 fg a2 d2 | egfa gfed | B2 AG GABc | d6 GA | B2 B2 c2 BA | Bdef g2 fg | efde BdAB | G6 :|  