Design a musical composition incorporating the alphabetic expression of the chosen structure and the provided melodic theme.
X:1
L:1/8
Q:1/4=120
M:4/4
K:D
['DFAF DFAF', '']  
X:1
L:1/8
Q:1/4=120
M:4/4
K:D
"D" DD FA df ed |"A" cc Ac"G" BB GB |"D" A>B A>G FAdf |"G" gg"D" fa"A7" ec"D" d2 :: 
[M:6/4]"D" fa (3aaa fd ef"G" gb (3bbb |[M:4/4]"D" fa (3aaa fd ef |"G" g2"D" fa"A7" ec"D" dd :: 
"D" DD FA df ed |"A" cc Ac"G" BB GB |"D" A>B A>G FAdf |"G" gg"D" fa"A7" ec"D" d2 :|"D" DFAF DFAF | 
"G" DGBG DGBG |"D" DFAF DFAF |"A" A,CEC A,CEC |"D" DFAF DFAF |"G" DGBG DGBG |"D" A>B A>G FAdf | 
"G" gg"D" fa"A7" ec"D" d2 |]  