You can download songs through all the music software, like Itunes or Rhapsody. Or, you can try www.songs.pk for other songs if you want.
If these songs are saved in your iPad, you can try this software, PrimoMusic. It helps to transfer music from iPad/iPhone/iPod to computer easily. Here is the link. www.primosync.com/support/how-to-transfer-music-from-ipad-to