I’ve heard the term used here, but I’ve never used any Nord stuff, so this is just from memory:
In “classic reset” a module is kept in the reset state as long as the reset line is high. That’s it.
The “Impromptu variation” is now the VCV standard, although it wasn’t originally. That is classic reset, except clocks are ignored if the occur any time after reset, up to 1 millisecond.
“Nord Reset” is totally different. A module is reset on the first clock that occurs after a low to high transition on the reset input.
Classic reset has the problem that if a clock is slightly delayed it will cause the sequence to begin at step 2 instead of step 1. Impromptu clock lockout prevents this. This is (now) well documented in the VCV specifications.
But there are still problems with this scheme. One is that it isn’t specified in the VCV manual if the reset it edge triggered or level sensitive. Another is that if the reset were to come in right in-between clocks the current step and the first step will be half duration. These problems all occur because in these reset schemes a reset pulse acts as a clock also.
With Nord reset protocol the clock is the clock, and the reset is the reset. The rhythm stays true to the clock, and clocks don’t need to be ignored. BUT – the reset must occur before the clock. If not it will not reset until the next clock – sort of the opposite of the problem with classic reset.
I don’t know which works better “in the real world”. Obviously classic clock will give terrible results. Both Impromptu and Nord reset can work, although I think Nord reset is used less often.
And of course it goes without saying that without good testing it’s very unlikely that anyone will programmer implement these correctly. I always had had many unit tests for this.
My old modules use Impromptu reset. If I were to do it again I would implement both and give the user a choice.