iPod classic syncing with new iMac

I have a iPod classic filled with my music that I synced with my old iMac. Will I lose my music that's on my iPod classic if I sync it with my new iMac on iTunes. I down loaded most of my music in iTunes on my new iMac. I just wanted to know that I can sync my iPod classic and get all my new and old songs on my iPod classic. I just didn't want to lose all my music on my iPod classic if I tried syncing it with my new iMac. Can you please tell me I can do this without losing anything on my iPod classic.