PHP uploading form problems

Im having problems with my uploading form using php I have created pages like this in the past but for some reason this one seems to be playing up I'm hoping i have just missed something so simple. Im trying to create and upload form to upload Wav, rar, zip and txt files and returning error on everything else.

If i try and upload a file which is not related to these it shows an error but if i try to upload a wav or a zip file it doesn't work i don't get any kind of error report but if i was to upload a .txt file it seems to work fine.

my html code is;

           <form action="<?php echo $site_url; ?>upload.php" enctype="multipart/form-data" method="post">
                <input type="hidden" name="upload" id="upload" value="upload" />
  <label for="invoice"><strong>Select Invoice Number</strong></label>

 <select name="invoice" <?php if (array_key_exists('invoice', $add_product_errors)) echo ' class="error"'; ?>>


<?php  while($row = mysqli_fetch_array($r)){ ?>
<option value="<?php echo $row[0] ; ?>" 
<?php if (isset($_POST['invoice']) && ($_POST['invoice'] == $row[0]) ) echo ' selected="selected"';
        echo ">" .$row[0]. "</option>\n"; ?>
        <?php } ?>
</select><?php if (array_key_exists('invoice', $add_product_errors)) echo ' <span class="error">' .$add_product_errors['invoice']. '</span>'; ?>
<label for="track"><strong>Upload File</strong></label>

<input type="hidden" name="MAX_FILE_SIZE" value="5120000" /> 
<input type="file" name="song" id="song" <?php if (array_key_exists('song', $add_product_errors)){ echo " class=\"error\" /> <span class=\"error\">" .$add_product_errors['song']. "</span>"; }else{    echo ' />'; if (isset($_SESSION['song'])){  echo " CURRENTLY '{$_SESSION['song']['file_name']}'"; } } ?>
  <input type="submit" name="upload_files" id="upload_files" value="Upload Files" />
      </form>

and my php script;

if(isset( $_POST['upload'])){
    if(is_uploaded_file($_FILES['song']['tmp_name']) && ($_FILES['song']['error'] == UPLOAD_ERR_OK)){

         $file = $_FILES['song'];
             $size = ROUND($file['size']/1024);
            if($size > 5120000){
              $add_product_errors['song'] = 'The File Size is too Big';
             }// END FILE SIZE


   $allowed_mime = array('audio/wav', 'audio/x-wav', 'application/x-compressed', 'application/x-zip-compressed', 'application/zip', 'multipart/x-zip', 'text/plain');
             $allowed_extensions = array('.wav', '.zip', '.rar', '.txt');
             $ext = substr($file['name'], -4);


             if((!in_array($file['type'], $allowed_mime))
      || (!in_array($ext, $allowed_extensions))
      ){
       $add_product_errors['song'] = "We Only accept .wav and .zip files please do not send .mp3 files";
       }// END IF WRONG EXT

                if (!array_key_exists('song', $add_product_errors)){

            $dest = "clients/" . $username[0] . "/" . $_POST['invoice'] . "/" . $file['name'];
        if(move_uploaded_file($file['tmp_name'], $dest)){
     //  $_SESSION['image']['new_name'] = $new_name; 
      $_SESSION['song']['file_name'] = $file['name'];
      $add_product['text'] = "
Files has successfully been moved
\n";
       }else{ 
        trigger_error('the file could not be moved.');
        unlink($file['tmp_name']);
       }// END if file is moved
        }// END  if file can be moved

    }elseif (!isset($_SESSION['song'])){
             switch ($_FILES['song']['error']){
        case 1:
        case 2:
          $add_product_errors['song'] = "File is too big 5GB Max";
          break;
        case 3:
          $add_product_errors['song'] = "the file was partially uploaded";
          break;
          case 6:
        case 7:
        case 8:
          $add_product_errors['song'] = "Couldn't upload due to a system error";
          break;
        case 4:
        default:
           $add_product_errors['song'] = "No file was uploaded"; 
           break;
          }//END OF SWITCH
    }
     if(empty($add_product_errors)){
    echo 'yes';
    $body = $username[0] . " has uploaded files in to " . $_POST['invoice'] . " Ready to start downloading and working on";
   //mail($site_email, 'file has been loaded',$body,'from:' .$site_email);

      //$_POST = array();
      //$files = array();

 unset($file,$_SESSION['song']);
     }



}//END IF $_POST UPLOAD

any help would be so much appreciated thank you