Why not using TimeMachine? It is doing everything in the background.
Or you might want to try to paid version of SuperDuper, that also allows for incremental backups (called SmartUpdate) for your whole disk.
Thank you so much! Sorry it took me a while to try things out, but thank you so much for your time and effort and super quick replies! I have SuperDuper paid version, but it only seems to clone the disk, rather than letting me do an incremental backup of just the folder which is on another disk. CarbonCopyCloner did exactly the job I wanted, so I'm very happy, and thankyou for including the link - I had everything I needed in a new york minute. I haven't looked into time machine - i only run it occasionally, my iTunes folder is the only thing I really need to keep on my computer.
I would like to say thanks again to both of you, I really appreciate that you take the time to help out a total stranger and semi-literate computer user!
All the best,