If you check on PSR Tutorial you can find out what Tyros3 styles were left off the Tyros4.

You can download the complete Tyros3 styles, which work in the Tyros4 unedited.

Some Tyros4 styles are re-worked Tyros3 styles...generally the intros/endings may be changed, and perhaps some of the new vocal sounds added.

It's simple...put all the Tyros3 styles (or Tyros2 or CVP-509) that you will find useful, in a folder, and you are good to go, as loading time is immediate, even from USB or HD.

All my S910 custom styles work great...sometimes I may need to alter an OTS, as the S910 lacks aftertouch, but otherwise, no issues.

Essentially, regarding styles, the Tyros4 is backwards compatible with the older series...registrations might need to be changed, but I think Michael Bedesem or Jorgan have programs to make it easy.

The Tyros3 sounds are all there on the Tyros4...some are in a Legacy folder, but, you aren't missing any sounds at all.

Ian