How to sync my device with itunes without replacing my backup?

I want to sync my ipod with my laptop to get my music into my ipod but I don't want to replace my iphone backup with my ipod

As I know, sync iPod will not replace your iPhone backup. Or you can set your iTunes to 'manually manage music and video', this will prevent iTunes sync iPod automatically, and you can drag and drop the songs you want from iTunes to iPod. Or you can use a third party software like this TunesGo, it's an alternative to iTunes, you can use it to upload media from computer to your iPod, and it will not delete any files on your iPod.
http://www.reviewstown.com/itunes-alternative.html