<ul class="sample-playlist">      
            <li data-author="Djmax"
            data-name="Danger"         
            data-url="http://mysite.ru/file/ebd106e2df6fd.mp3"
            data-track-id="27898"    
            class="play">
                  </li>
            <li data-author="DjПупкин"
            data-name="Don"        
            data-url="http://mysite.ru/file/ebd10dtytdeddb7df6.mp3"
            data-track-id="27899"  
            class="play">
                  </li>
            <li data-author="Вася"
            data-name="Мой твой"           
            data-url="http://mysite.ru/file/ebdtddthdtheddf6fd.mp3"
            data-track-id="27846"    
            class="play">
                  </li>
            .......
</ul>

<ul class="sample-playlist">    
     <div class='music'>
            <li data-author="Djmax"
            data-name="Danger"         
            data-url="http://mysite.ru/file/ebd106e2df6fd.mp3"
            data-track-id="27898"    
            class="play">
                  </li>
    </div>
    <div class='music'> 
           <li data-author="DjПупкин"
            data-name="Don"        
            data-url="http://mysite.ru/file/ebd10dtytdeddb7df6.mp3"
            data-track-id="27899"  
            class="play">
                  </li>
    </div>
    <div class='music'> 
           <li data-author="Вася"
            data-name="Мой твой"           
            data-url="http://mysite.ru/file/ebdtddthdtheddf6fd.mp3"
            data-track-id="27846"    
            class="play">
                  </li>
    </div>        .......
</ul>

var ul = document.querySelector('ul.sample-playlist');
var lis = ul.querySelectorAll('li');
for(var i = 0; i < lis.length; i++) {
  var div = document.createElement('div');
  div.className = 'music';
  div.appendChild(lis[i]);
  ul.appendChild(div);
}