Compose a piece that embodies the quintessence of Bach's signature sound.  
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 bass 
%%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
 D C C D | E D C B, | !fermata!A,2 z C | D E D ^C | !fermata!D2 z G | D/E/ F E D | %6
 !fermata!E2 z D | C D E D | C B, !fermata!A, C | D E D ^C | !fermata!D4 |] %11
V:2
 A, A, A,3/2 G,/ | G,/ C B,/ A,3/2 ^G,/ | !fermata!E,2 z A, | A, _B,/A,/ A, A, | %4
 !fermata!A,2 z D/C/ | _B, A,/ D ^C/ D/D,/ | !fermata!A,2 z A,/^G,/ | A,/ C B,/ C B, | %8
 B,/ A, ^G,/ !fermata!E, A, | A, _B, A, A, | !fermata!A,4 |] %11
V:3
 F, F, E,/F,/ D, | C,/E,/ F, ^F, B,,/E,/4=D,/4 | !fermata!C,2 z E, | F,/D,/ G,3/2 F,/ E, | %4
 !fermata!F,2 z G, | G, A, A,3/2 G,/ | !fermata!^C,2 z F, | E, G, G, F, | %8
 E, E,/>D,/ !fermata!C, E, | F, G,3/2 F,/ E,/G,/ | !fermata!^F,4 |] %11
V:4
"Dm" D,,/E,,/"F" F,,/G,,/"Am" A,,"Bm" B,, |"C" C,"Dm" D,"D#dim7" ^D,"E" E,/E,,/ | %2
"Am" !fermata!A,,2 z"Am" A,,/G,,/ |"Dm/F" F,,"C#dim7" ^C,,"Dsus4" D,,"A" A,, | %4
"Dm" !fermata!D,,2 z"Gm/Bb" _B,,/A,,/ |"Gm" G,,"Dm" D,,"Asus4" A,,"Bb" _B,, | %6
"A" !fermata!A,,2 z"Dm" D,, |"Am" A,,"Gsus4" G,,"C" C,/B,,/"Bm7b5/A" A,,/^G,,/ | %8
"Am" A,,"Esus4" E,,"Am" !fermata!A,,,"Am" A,,/G,,/ | %9
"Dm/F" F,,/E,,/"Em7b5/D" D,,/^C,,/"Dsus4" D,,"A" A,,, |"D" !fermata!D,,4 |] %11  