index.js

//var numOfDrumBtn = document.querySelectorAll(".drum");
for(var i = 0; i < document.querySelectorAll(".drum").length; i++){
  document.querySelectorAll(".drum")[i].addEventListener("click",function(){
    var buttoninnerHTML = this.innerHTML;
    makeSound(buttoninnerHTML);
  });
}

document.addEventListener('keypress', (e) =>{makeSound(e.key);} );

function makeSound(key){
  switch(key) {

    case 'w':
      var tom1 = new Audio('sounds/tom-1.mp3');
      tom1.play();
      break;

    case 'a':
      var tom2 = new Audio('sounds/tom-2.mp3');
      tom2.play();
      break;

    case 's':
      var tom3 = new Audio('sounds/tom-3.mp3');
      tom3.play();
      break;

    case 'd':
      var tom4 = new Audio('sounds/tom-4.mp3');
      tom4.play();
      break;

    case 'j':
      var snare = new Audio('sounds/snare.mp3');
      snare.play();
      break;

    case 'k':
      var crash = new Audio('sounds/crash.mp3');
      crash.play();
      break;

    case 'l':
      var kick = new Audio('sounds/kick-bass.mp3');
      kick.play();
      break;

    defualt:
      console.log(this);

  }
}

document.addEventListener('keydown', borderColorAdd);

function borderColorAdd(e){
  document.querySelector('.'+e.key).classList.add("color-change");
}

document.addEventListener('keyup', borderColorRemove);

function borderColorRemove(e){
  document.querySelector('.'+e.key).classList.remove("color-change");
}