HT1238: About iPod Reset UtilityLearn about About iPod Reset Utility
Currently Being ModeratedMar 17, 2013 1:24 PM (in response to arnab banerjee)
If your songs were purchased from the iTunes Store, you can go to the Purchased screen (in the iTunes Store), while logged in with your Apple ID (the one used to purchase the songs), and re-download any previous purchase.
Otherwise, if you do not have a backup of your song files, they are lost. If you do have a backup, you just need to drag the song files (or the folder containing the song files) to the iTunes window.