The easist way has to be using a PC and USB File Mode.

If not, you'll have to have a backup device of suitable capacity (i.e. bigger than the internal drive in the Tyros) and a USB interface box such as this: http://www.pixmania.co.uk/uk/uk/53670/art/ngs/usb-to-usb-transfer-box.html

You need an interface box to because with USB one end has to be "host" and everything else (even on a daisy chain) has to be a device. Usually the PC will be a host. The USB interface box acts as a host to the two devices plugged into it and manages transfer of data between the two devices. The interface boxes I've heard about (but never used) all seem to be "One shot" systems; connect your two devices (in your case the Tyros and the backup device) and press a button to transfer all data on one device onto the other one. I don't think there's any selectability build into the operation.

Doing a bit of Googling it looks more intelligent transfer devices are being created, at rather more expense of course: http://us.gizmodo.com/gadgets/portable-media/hitch-usb-transfer-device-147703.php

Hope this helps!

John