Can't add songs to iphone without it erasing my iphone?

Okay, so itunes, being as stupid as it is, isn't letting me put songs on unless I let it wipeout my whole entire phone, because apparently you can't download from more than one library at a time. Is there any way I can backup all of my music? I can't really figure out how to… I don't really care about my apps, though, I just… NEED my music.xc

I don't know if it's the same on an iPhone as it is on an iPod but when I plug in my iPod touch in there's an option to manually manage music and video on the iPod's main screen in iTunes. If you do that it doesn't wipe it clear.

EDIT~
fixed misspellings.

"apparently you can't download from more than one library at a time"

If you believe that, then the mistake is your own and the stupidity at work is not iTunes's or Apple's. I've downloaded to my iPod from more than one library, and just a short while ago, I downloaded to my son's iPod Touch songs that were on his sister's library. Your mistake seems to be that you want to sync music from more than one library. Like 99% of the iPod owners who post questions here, you seem to think that syncing is the only way to put music on an iPod. It isn't. You can set for manual management of music and video and simply drag and drop your music. This is a bit more labor intensive, not accounting for the fact that I've never wiped out my entire music collection. If you insist on syncing, then you run the risk of losing whatever music is not on your computer (especially if you're like all those iPod owners who simply never thinks to back their music up to CD or flash drive). That's what syncing does because that's whay "sync" means - to link two devices and make sure that there are no differences between them. This is an old and basic feature of iPods, yet so many new iPod owners just don't get it and blame iTunes or Apple or Bill Gates for everything they've never bothered to learn about iPods.