Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
M:4/4
K:G
['B2 Bc B3 G', 'E2 FG']  
X:1
L:1/8
M:4/4
K:G
 B2 Bc B3 G | A3 G FG FE | B2 Bc B3 G | A2 GA F4 :: E2 FG A3 B | A2 GF Bc B2 | E2 FG A2 BA | 
 G2 EA AG FG | E2 FG A3 B | A2 GF Bc B2 | E2 FG A2 BA | G2 FG E4 :|  