How do you put music on iphone from different computer without erasing all music?

Connor :
I know you have to put it into manual mode, but whenever i put it in manual mode it says something about updating the iphone settings and to do that i have to sync it with that computer and erase all of the music on my iphone, what do i do?

Joeyyyy :
as far as i know or remember, it's just not possible right now.

simply cos the iPhone (or iPod) could have music that was bought off iTunes with DRM protection...

the only suggestion i could give is to just put all the songs from the other computer onto a usb stick or cd, and transfer them over to the new computer. otherwise im afraid, apple just don't allow it.

Kevin L :
Pop into iTunes and choose File --> New Playlist. Now rename it to something logical: I use "iPhone Sync":

Now you can just drag and drop music from your iTunes library (in iTunes, needless to say) into this new playlist. When you're ready, you'll see a bunch of music happily ensconced in the playlist (remember, it's all just "pointers": the actual music files are still safely in the main music library, so if you delete something from a playlist , you haven't deleted the original music file itself):

At this point, you need to plug in your iPhone if you haven't already done so. It'll pop up the usual summary screen:

Now click on the "Music" tab and you'll see that you can select "sync playlist". Do that, then select the new iPhone sync playlist you've created

Now click "Sync" in iTunes and it'll synchronize your playlist with the iPhone music library and next time you click on that ole' "iPod" button on the iPhone, your selections from you music library will be present

twilightgirl :
you cant APPLE you cn only use one computer but if you get music off ur phone direct time its that on one computer