Craft a melody that reflects the core principles 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 treble 
%%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 G | G G A G | c d !fermata!c2 | B d e d | B A !fermata!G G | c B d A | G E !fermata!D D | %7
 A A A B | c A G/A/ B | A2 G G | G2 !fermata!G2 |] %11
V:2
 z3 D | E E F G | A B !fermata!A2 | G G G ^F | G ^F !fermata!D E | E/^F/ G G F | %6
 E/D/ ^C !fermata!A, D | D A/G/ ^F ^G | A =F E/^F/ G | G =F F/E/ E | E D/C/ !fermata!D2 |] %11
V:3
 z3 B, | B, C C C/D/ | E F !fermata!E2 | E D C/B,/ A, | B,/C/ D !fermata!B, B, | C D D D/C/ | %6
 B, A,/G,/ !fermata!^F, F,/G,/ | A,/B,/ ^C D D | E C C D | D/A,/ D/C/ B, C | %10
 C B,/A,/ !fermata!B,2 |] %11
V:4
 z3"G" G, |"Em" E,"C" C,"F" F,"C/E" E, |"Am" A,"G#dim7" ^G,"Am" !fermata!A,2 | %3
"Em" E,"G/B" B,,"C" C,"D" D, |"G" G,"D" D,"G" !fermata!G,,"Em" E, | %5
"Am" A,,"G" G,,/A,,/"G/B" B,,/C,/"D" D, |"Em/G" G,,"A" A,,"D" !fermata!D,"D" D,/E,/ | %7
"D/F#" ^F,/G,/"A" A,/B,/"D7/C" C"G#dim/B" B, |"Am" A,"F/A" A,,/B,,/"C" C,"G/B" B,,/C,/ | %9
"Dsus4" D,"Dm7/C" C,/D,/"Em" E,"C/D" D,/C,/ |"C/G" G,2"G" !fermata!G,,2 |] %11  