Craft a musical composition that adheres to the specified musical theme and letter-based structure.
X:1
L:1/8
Q:1/4=150
M:2/4
K:G
['AG F2']  
X:1
L:1/8
Q:1/4=150
M:2/4
K:G
 GA Bc | dc BA | G2 c2 | cB AG | F2 B2 | BB AG | F2 G2 | G2 z2 ||  