I know this works on my PSR-E433, and likely works with all of its successors. Let me know if this is not the case...
One very useful thing about how the registration banks work on the E400 series keyboards is that you can "pre-select" a different bank than the one that you are currently playing from, without it changing the currently playing sound, so that at the appropriate point in the song you're playing, all you have to do is hit the desired registration button to get the new registration from the pre-selected bank.
Here's an example. As one of the eight banks on my E433, I have a bank of four orchestral settings, such as strings and brass -- It is bank 3 on my keyboard. And I have a bank of rock sounds, like rock organ, electric guitar, and synth -- This one is bank 5. I play a particular song that starts out with orchestral strings, but then goes to the rock synth sound. So, before I start playing, I select bank 3, my orchestral bank, and then select my strings registration. Now, before I start playing, I then select bank 5, my rock sounds bank -- but I DON'T yet select a registration. So, even though I changed the bank from 3 to 5, my originally selected strings sound from bank 3 is still active. Therefore, I can start playing the song with the strings, and then when it's time to go to my rock synth sound, I just have to hit one button -- the registration button for that sound, since the new bank had already been selected -- instead of having to change both the bank and select the new registration all at once.
In some keyboards, by selecting a different bank, it automatically changes the sound to a registration or preset in that bank, so that you could not use this technique. This is true with my Roland Gaia synth, which has 8 banks of 8 presets. If I have, say, the 8th preset of bank 1 selected, and then I change to bank 2, the keyboard will now play the sound of the 8th preset of bank 2 right away, just by changing the bank.
The ability to change and pre-select a bank on the E400 keyboards, without it changing the actual sound until you hit a registration button, gives you a little more flexibility with the fairly limited number of registrations available.
