How do I add new songs to my ipod without erasing what is already on it?

[ix3mudvayne]

So a few months ago, the motherboard in my laptop fried and I lost everything that was on it. I have a little over 1000 songs on my ipod already, but I obviously want to put more on it but I don't know how I can add new songs to it without erasing everything that is already on it. Help?