How to sync your iPod/iPhone without erasing existing music?

I lost the majority of my music on iTunes and it won't restore it all. I want to know how to sync my iPod and iPhone to iTunes without having to erase my existing music that is already on my iPhone/iPod.

I'd also like to know if there's any way you can sync music to iTunes from your iPod/iPhone?

It should have the option to sync all the music from your iPod to iTunes but that might include erasing everything you currently have on your iTunes. Another way is you could do the home sharing thing on iTunes, where if you download iTunes onto a second computer and connected your iPod and sync all the music off your iPod on to the empty iTunes then click home sharing. Providing iTunes is open on both computers using home sharing you can take the music off and copy it to the other and vise versa. Also you don't have to do copies, it tells you on home sharing what songs both computers have and which ones that one has but the other doesn't so you can just choose whichever you want. Hope this helped.

On you ipod tab, click manually manage music. And now you can put mysic onto your ipod from any itunes computer.
to get music out of an ipod is alittle tricky because apple sees this as a no no.look on google though, there are programs that can take the music put for you