Here's the spiffeh:
I've got a working script, but it involves renaming your files.
Now, this script may not be what you want, provided the renaming, and if not, I'm sure that someone else can develop one/there may be one that exists.
Here is what I have:
$id = $_GET['id'];
$filename = "download/file_".$id.".mp3";
header("Content-disposition: attachment; filename=".$filename."");
That should be your get.php file.
The files are in a subfolder called download and each file is named file_#.mp3 with the # sign being the ID number.
To say, if I have file_1.mp3, file_2.mp3, and file_3.mp3 and I want to download file_2.mp3, then I go to http://www.domain.com/get.php?id=2 and it will grab the file_2.mp3 from inside of the download folder, which remains unseen.
I'll look and see what other scripts I can find. My friend developed one similar to this and I think that it would work perfect. Until I can, this could serve your purpose.