Songs to my iphone from a different itunes

Hello,

somebody please help me! I originally set my syncing settings to sync automatically. However, I decided I just want to manage my music manually, so I changed it to manually manage music. But when I connect my iphone to a different itunes library, it still doesnt allow me to copy songs from that different itunes lib to my iphone. Is there another way of putting songs in my iphone without having to first copy it on my itunes and then sync?

I already tried changing the setting to manually manage. I even tried to just not sync music only.
Does anybody know how to go about this please? thanks!