After playing in the second octave, I have problems playing the lowest note of the whistle if I have to make a fast jump and I am not sure what to do about it - in slower tempo it all works fine. I have examined several whistles and found out that tweaked whistles have faster response to the change of the air flow. Does this really depend on the whistle?
Some of it may be the whistle, some may be technique. How’s that for an evasive answer? 
Seriously, some whistles do make the transition much more easily. What type of whistle are you playing?
open the throat faster and slow the airflow --try that-------------you can feel your throat /wind requirements change as you move up the scale
I play Generation whistles. Bb is tweaked and I can switch from higher notes to lower easier on it. Also a Generation D, not tweaked, my main whistle. Also I have a tweaked Walton, but it’s lowest note requires so small a flow, that it also works not very well.
Louigi,
A good drill is to play each note of the two octaves interspersed by the lowest note.
For instance, on a D whistle (where italics = second octave):-
D D; D E; D F#; D G; D A ; D B; D C; D C#; D D;
D E; D F#; D G; D A; D B; D C; D C#; D D+
and back down the same way.
15 minutes of this 4 times a week for 4 weeks should do it for you I reckon.
Thanks, I will start right away!
One of the things I found out was that it’s easier to play the lowest if you don’t tongue it.
One of the things I found out was that it’s easier to play the lowest note if you don’t tongue it.