Compose a piece of music that follows both the given musical theme and the letter-based structure provided.
X:1
L:1/8
Q:1/4=115
M:4/4
K:Bb
['B,D F3']  
X:1
L:1/8
Q:1/4=115
M:4/4
K:Bb
 B,D |"Bb" F3 G F2 B2 |"Eb" B3 G"Bb" F2 B,D | F3 F GF DB, |"F" C4 z2 B,D |"Bb" F3 G F2 B2 | 
"Eb" B3 G"Bb" F2 Bc | d3 B"F7" c2 d2 |"Bb" B4 z2 || Bc |"Bb" d3 B"F7" c2 d2 |"Eb" B3 G B2 G2 | 
"Bb" F3 F GF DB, |"F" C4 z2 B,D |"Bb" F3 G F2 B2 |"Eb" B3 G"Bb" F2 Bc | d3 B"F7" c2 d2 |"Bb" B6 |]  