Bende türkçe veriyim, örnek olsun 
<script language="javascript" type="text/javascript">
function Secildi(str)
{
    var sarkilar = '<select name="sarkilar">';
    
    switch(str)
    {
         case '1': sarkilar += '<option value="1">Beatles Sarki1</option><option value="2">Beatles Sarki2</option><option value="3">Beatles Sarki3</option>'; break;
         case '2': sarkilar += '<option value="1">HIM Sarki1</option><option value="2">HIM Sarki2</option><option value="3">HIM Sarki3</option>'; break;
         default: sarkilar += '<option value="0">Grup Seçin</option>'; break;
    }
    
    sarkilar += "</select>";
    document.getElementById("sarkilar").innerHTML = sarkilar;
}
</script>
</head>
<body>
<form action="" method="POST">

    <select name="grup" onchange="Secildi(this.value);">
        <option value="0">Seçin</option>
        <option value="1">Beatles</option>
        <option value="2">HIM</option>
    </select>
    
    <div id="sarkilar">
        <select disabled="disabled">
            <option value="0">Grup Seçin</option>
        </select>
     </div>

</form>