Devise a musical masterpiece using Bach's signature techniques.  
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 A | c A _B A | G G !fermata!F A | B c d c | B2 !fermata!A E | F F G G | A A !fermata!F D | %7
 E F G F | E2 !fermata!D z |] %9
V:2
 z3 F | G3/2 F E/ F | F3/2 E/ !fermata!C A | A/^G/ A3/2 G/ A | A ^G !fermata!E ^C | %5
 D D D/=B,/ ^C/D/ | E/D/ E/^C/ !fermata!D A,/B,/ | =C C ^C D | D ^C !fermata!A, z |] %9
V:3
 z3 D | C C _B, C | D C/>_B,/ !fermata!A, C | F E D E | F E/D/ !fermata!^C A, | A, A, G, _B, | %6
 A, A, !fermata!A, F, | G, A,/F,/ _B,/G,/ A, | A,/E,/ A,/G,/ !fermata!^F, z |] %9
V:4
 z3"Dm" D, |"C/E" E,"F" F,"Gm" G,"F/A" A, |"Gm7/Bb" _B,"Csus4" C"F" !fermata!F,"F" F,/E,/ | %3
"Bm7b5/D" D,"Am/C" C,"Bm" B,,"Am" A,, |"Bm7b5/D" D,"E" E,"A" !fermata!A,,"A" A,, | %5
"Dm" D,,/ D, C,/"G/B" =B,,/ E, D,/ |"A/C#" ^C,/B,,/"A/C#" C,/A,,/"Dm" !fermata!D,"Dm" D, | %7
"C" C,/_B,,/"F/A" A,,"C#dim7/E" E,,"Dm/F" F,,/G,,/ |"Asus4" A,,2"D" !fermata!D, z |] %9  