Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/4
Q:3/4=100
M:6/4
K:Fdor
['B A G F', 'c B']  
X:1
L:1/4
Q:3/4=100
M:6/4
K:Fdor
 c | A F a g2 =e | f c _d c2 B | A G F _d c B | A G F =E2 c | A F _d B2 G | E C c A2 F | 
 _D B, B A G F | F3- F2 :: c | c B =A c e c | _d B =A B2 B | B G _A B _d B | c A G A2 c | 
 _d c B A G F | =E G B _d f a | c B A G F =E | F3- F2 :|  