Construct a tune that reflects the essence of Bach's compositions.  
X:1
T:Music21 Fragment
T:Music21 Fragment
T:Music21
C:Music21
%%score 1 2 3 4
L:1/4
M:4/4
K:C
V:1 treble 
%%MIDI program 0
%%MIDI control 7 100
%%MIDI control 10 64
V:2 treble 
%%MIDI program 0
%%MIDI control 7 100
%%MIDI control 10 64
V:3 bass 
%%MIDI program 0
%%MIDI control 7 100
%%MIDI control 10 64
V:4 bass 
%%MIDI program 0
%%MIDI control 7 100
%%MIDI control 10 64
V:1
 z3 C/D/ | E F G G | F E !fermata!D G | A B c B/A/ | A2 !fermata!G C/D/ | E F G G | %6
 F E !fermata!D G | A B c B/A/ | A2 !fermata!G G | c B A G | F E/D/ !fermata!D G | F E D/E/ F | %12
 E D !fermata!C z |] %13
V:2
 z3 G, | C C C C | C/B,/ C !fermata!B, D | D ^F G/D/ D/E/ | E ^F !fermata!D G, | C C C C | %6
 C/B,/ C !fermata!B, D | D ^F G/D/ D/E/ | E ^F !fermata!D E | A G3/2 F E/ | %10
 E/D/ C !fermata!B, _B, | _A, G, F,/G,/ A, | G,/ C B,/ !fermata!G, z |] %13
V:3
 z3 E,/F,/ | G, A, _B, A,/G,/ | A, G, !fermata!G, B, | A, D G,/A,/ B,/C/ | %4
 C/B,/ A, !fermata!B, E,/F,/ | G, A, _B, A,/G,/ | A, G, !fermata!G, B, | A, D G,/A,/ B,/C/ | %8
 C/B,/ A, !fermata!B, C | E E E/D/ D/B,/ | C/G,/ G, !fermata!G, E,/D,/ | C, ^C, D, D, | %12
 E,/>F,/ G,/D,/ !fermata!E, z |] %13
V:4
 z3"C" C,, |"C" C,"F/A" A,,"C7/E" E,,"Am" A,, |"Dm7" D,,"C/E" E,,/F,,/"G" !fermata!G,,"G" G, | %3
"D/F#" ^F,"Bm/E" E,/D,/"C/E" E,/F,/"G" G, |"Am/C" C,"D" D,"G" !fermata!G,,"C" C,, | %5
"C" C,"F/A" A,,"C7/E" E,,"Am" A,, |"Dm7" D,,"C/E" E,,/F,,/"G" !fermata!G,,"G" G, | %7
"D/F#" ^F,"Bm/E" E,/D,/"C/E" E,/F,/"G" G, |"Am/C" C,"D" D,"G" !fermata!G,,"C" C,/B,,/ | %9
"Am" A,,"Em" E,,"Fmaj9" F,,"Gpower" G,, |"Fmaj7/A" A,,/B,,/"C" C,"G" !fermata!G,,"Edim/G" G,, | %11
"Fm/Ab" _A,,"A7" =A,,"Bb" _B,,"Bdim7" =B,, |"C" C,"Gsus4" G,,"C" !fermata!C,, z |] %13  