как то проглядел твой пост в непрочитанном, сделал на чистом js
<html>
<head>
<title>JS</title>
<style>
#tracklist {
padding: 2px;
margin: 2px;
border: 1px dotted black;
}
a, span {
text-decoration: none;
color: red;
cursor: pointer;
}
</style>
<script type="text/javascript">
function tracklist_handler(element_id, mode) {
if (mode == 'add') {
document.getElementById(element_id).innerHTML += '<div><input type="text" name="tracklist[]" value="" /></div>'
} else {
var children = document.getElementById(element_id).childNodes;
document.getElementById(element_id).removeChild(children[children.length-1]);
}
}
</script>
</head>
<body>
<form method="post" action="">
<div id="tracklist">
<div><input type="text" name="tracklist[]" value="" /></div>
</div>
<div style="text-align:center;">
<span id="plus" onclick="javascript:tracklist_handler('tracklist', 'add')">+</span> 
<span id="minus" onclick="javascript:tracklist_handler('tracklist', 'remove')">-</span>
</div>
</form>
</body>
</html>