вот эта ЧЕРНАЯ ГОРИЗОНТАЛЬНАЯ полоска, смотри скриншот: https://yadi.sk/d/FejQ4LyoT5cEuA

как ее убрать?

/* audio player */
.audio-player {
  margin: 50px auto;
  max-width: 800px;
}

.audio-player-inner {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.audio-tracklist {
  display: flex;
  flex-direction: row;
  justify-content: center;
  align-items: center;
  flex-wrap: nowrap;
  margin: 0;
  padding: 0;
  list-style: none;
}

.audio-track {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  margin-right: 20px;
  margin-bottom: 20px;
  max-width: 300px;
  text-align: center;
  height: auto; 
  position: relative;
  transition: transform 0.3s;
}

.audio-track:hover {
  transform: scale(1.05);
}

.audio-track-image {
  width: 100%;
  height: 0;
  padding-bottom: 100%;
  position: relative;
}

.audio-track-image img {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  filter: brightness(100%);
  transition: filter 0.3s;
}

.audio-track:hover img {
  filter: brightness(70%);
}

.audio-track-info {
  width: 100%;
  margin-top: 10px;
  text-align: center;
}

.audio-track-info h4 {
  margin-top: 0;
  font-size: 18px;
  font-weight: bold;
}

.audio-track-info p {
  margin-bottom: 0;
  font-size: 14px;
}

.audio-player-wrapper {
  opacity: 0;
  transition: opacity 0.3s;
}

.audio-track:hover .audio-player-wrapper {
  opacity: 1;
}

.audio-player-button {
  display: flex;
  justify-content: center;
  align-items: center;
  border: none;
  background: none;
  cursor: pointer;
  margin: 0 auto;
}

.audio-player-icon {
  font-size: 24px;
  margin-top:-250px;
  color: #333;
  position: relative; /* добавить свойство position */
  z-index: 1; /* добавить свойство z-index */
}

.progress-bar {
  width: 100%;
  height: 5px;
  -webkit-appearance: none;
  appearance: none;
  background: #ddd;
  outline: none;
  cursor: pointer;
}

.progress-bar::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 15px;
  height: 15px;
  border-radius: 50%;
  background: #333;
  cursor: pointer;
}

.progress-bar::-moz-range-thumb {
  width: 15px;
  height: 15px;
  border-radius: 50%;
  background: #333;
  cursor: pointer;
}

.progress-time {
  font-size: 12px;
  margin-left: 10px;
  color: #666;
}

input[type=range]::-webkit-slider-runnable-track {
  background: transparent;
  border: none;
}

index:
<!-- audio player -->
<div class="audio-player">
  <div class="audio-player-inner">
    <div class="audio-tracklist">
      <% tracks.forEach((track, index) => { %> 
        <div class="audio-track">
          <div class="audio-track-image">
            <img src="/img/<%= track.image_filename || 'default-track-image.png' %>" alt="<%= track.title %>">
          </div>
          <div class="audio-track-info">
            <h4><%= track.title %></h4> 
            <p class="album-title"><%= track.album_title || "No Album" %></p>
          </div>
          <div class="audio-player-wrapper">
            <button class="audio-player-button" onclick="togglePlay(<%= index %>)">
              <i class="audio-player-icon fa fa-play"></i>
            </button>
            <audio id="audio-<%= index %>" src="/tracks/<%= track.filename %>" ontimeupdate="updateProgress(<%= index %>)"></audio>
            <input type="range" id="progress-bar-<%= index %>" class="progress-bar" value="0" onchange="setProgress(<%= index %>, this.value)">
            <span class="progress-time" id="progress-time-<%= index %>">0:00</span>
          </div>
        </div> 
      <% }); %>
    </div>
  </div>
</div>
<!-- end -->