[HELP] Midi button LED control code.

Other Hardware LEDs and Multiplexing
16

Just as an exercise I reduced your code to simply this:-

// Push Button to MIDI by Grumpy Mike - May 2018
// Push button wired between input and ground
#include <Bounce2.h>

const int channel = 1;
const byte pinNumbers[] = {16,20,0,4,15,19,1,5,14,18,2,6,13,17,3,7,24,11,12,23,10,9};
Bounce pushButton[22];
byte velocity = 99;

void setup() {
  for(int i = 0; i<22; i++){
    pushButton[i] = Bounce(pinNumbers[i], 5);
    pinMode(pinNumbers[i], INPUT_PULLUP); 
  }
 }

void loop() {
 for(int i = 0; i<22; i++){
  pushButton[i].update();
  if (pushButton[i].fallingEdge()) {
    usbMIDI.sendNoteOn(61+i, velocity, channel); // or change 61 to 81 for original note 
  }
  if (pushButton[i].risingEdge()) {
    usbMIDI.sendNoteOff(61+i, 0, channel); // or change 61 to 81 for original note
  }
 }
}

However, your code puzzled me. If you want a 4 by 4 matrix arrangement why have you defined 22 push button inputs?
Also the comment by the note values you send say things like "// 61 = C#4" when you actually are sending note number 81. Why is this?