Develop a musical piece using the given theme and incorporating the letter-based structure provided.
X:1
L:1/8
M:4/4
K:F
['gf e2']  
X:1
L:1/8
M:4/4
K:F
 e |"F" f2 fa"C" gf e2 |"F" fefa"C" gf e2 |"F" f2 fa"Gm" gfed |"C" c6 de |"F" f2 fa"C" gf e2 | 
"F" fefa"C" gf e2 |"Bb" b2 a2"C" gf e2 |1"F" f6 c :|2"F" f6 DE |:"F" F2 cF"Dm" FdFF | 
"F" cFFd"Dm" FF c2 |"F" f2 fa"Gm" gfed |"C" c6 DE |"F" F2 cF"Dm" FdFF |"F" cFFd"Dm" FF c2 | 
"Bb" b2 a2"C" gf e2 |"F" f6 z2 :|  