For the first time (I believe) with a Yamaha arranger, you will be able to buy sound packs like you can style packs direct from Yamaha, thus expanding the number of sounds onboard. (You will probably need to add more memory though)
This is due to the standard hard disk and faster interface. (Expect between 15 – 18 times faster loading from the hard disk)
The first to be introduced is the Vocal pack. (Pricing and availability is yet to be determined)

Bill