OK. I see this function is on Page 42 of the Tyros 4 Owner's Manual.
Doesn't look like it's anything really significant. I'm sure you can change the
type of REVERB you have and
how much reverb you have got in other ways. And changing the speed of the rotating speaker effect (slow/fast) I'm sure can be done elsewhere too.
What I would like to know (from anyone who has a Tyros 4) is if:
..
(a) you can change the speed of the 'fast' setting and make it much slower. So eg. you could change the tremolo from 'slow' to something a lot slower than the 'default' fast.
.. and
(b), is it possible to switch more gradually from a 'slow' to a 'fast' speed ie. so it isn't
instant. On the Farfisa organ I had, it had an internal Leslie speaker (a proper one) so, being mechanical, changing from one to the other was a
gradual process. And to my mind that sounded really good!