Is a tunable whistle or flute REALLY necessary? When playing with others everyone says that you MUST have a tunable whistle or flute in order to tune up with them. Why can’t everyone just be concert pitch?
Reminds me of Rodney King’s statement… “Why can’t we all just get along”.
I think the answer is…
'cause
…john
Tell everyone to be at concert pitch.
And see what happens.
Welcome to the forums, gerard. 
I feel like a Jerk 
Welcome!
I don’t need tunable whistles and actually
prefer untunable whistles. I play with others
a fair amount and I never touch the tuning
slide on my tunable whistles. I never
have any trouble with untunable whistles.
However a tunable flute is essential.
Sometimes I have to tune my flute.
(However maybe that’s because I
have a slide; these move a lot easier
on flutes than on whistles.)
same hear-----------
I generally play at worship Sunday mornings. One of the instruments is a baby grand piano, and the tuning on that is not the same week to week.
“Excuse me, could you please tune your piano to my whistle?”
I usually need to tune the whistles sharp for Sundays, where they are more at makers’ in-tune line for ensembles with instruments at A=440.
Some folks also play with reeded instruments, such as the concertina, which cannot be tuned.
Pitch on a whistle can also noticeably change with temperature. A cold whistle tends to play flat until warmed, and then can be annoyingly sharp once warmed up. Some players also tend to play flat or sharp depending on how much they “lean in” to the whistle while playing. I tend to play sharp once our session gets rolling. The majority of whistles are, or can be made tuneable anyway. Even as a gesture to your session-mates, a tuneable whistle is a plus.
Mike
As has been mentioned, when you play in a session etc. some folks will have instruments that can’t be tuned, and everyone else tunes to what they have for D etc. Since this is (usually) folk music, being at concert pitch isn’t required or even expected. But you can be off only so much and still sound OK together. A whistle can be off a fair amount as long as another whistle or r-----der isn’t also playing. If they are then the two fipple flutes need to be in tune with each other more than they need to be in tune with the rest of the gang. Especially in the upper octave. I have had to quit playing at times it was so painful.
As for whistle dynamics, the speed of sound changes with temperature and humidity. So, the tune of your whistle will change depending on where you are playing it. But the fiddle sitting next to you won’t, so you might want to adjust your whistle if you have different ambient conditions to put it back where you want it. Or not. It depends on what everyone else is doing.
I have 7 non-tunable whistles. They are quite well in tune, except for my Generations. First of all, does it bother me? Well not till so far. But I must say, I have an Overton low D where the fipple has been replaced once and now the pitch is somewhat different from the others, not very noticable but still. If you play in a band, the pitch of the instruments in the band normally is between 140 and 144. But if one is playing on 140 and the other on 144, it can be heard. In our band the others have to go with my whiste, that can be done, but playing somewhere else it could be useful to have a tuned whistle so you can change the pitch.
Lets say everyone is in concert pitch… are you sure your non-tunable whistle is in tune that night?
Besides as others have pointed out, with some instruments it is impossible or at least impractical to tune them at a session. Tunning an Accordion or a Concertina is an operation that could take a week and a machine shop! Meanwhile, tunable whistles are pretty easy to come by, so its just polite to tune the whistle. 
Just ask the box or concertina player for an A (BTW, they are usually pretty close to spot on in tuning), they will be happy to give it.
–
Bill
Gerard mentioned in his original post about playing with others. The tunables would be very nice to have in that scenario. Realistically however, given the ‘collections’ of whistles we tend to accumulate over time, how many of our whistles really need to be tunable? How much of our whistle playing time is actually spent playing with others? I bet many spend more time playing alone practicing or just having fun. In that case the simple low maintenance non tunable would work just fine…
Would the question arise if tunable and non tunable cost the same? As far as maintenance goes, I find the tunable whistles easier to maintain because you can take them apart to clean them. Cheers, Cyril.
Very true Cyril, Low cost good… expensive baaaad
Seriously though you are right that two pieces are easier to clean, and I’m in the ‘clean frequently’ camp when it comes to whistles. On some kinds of whistles though,ie; those with o-rings, teflon tape, fine string or other kind of “gasket” material in the slide, there is always a chance that the material will get worn or damaged when the whistle is taken apart.
After cleaning, my Copeland whistles just require a smear of cork grease on the tuning slide. My Overtons require a lilttle teflon tape from time to time. Thin Weasel some cork grease. The Sweatheart has a corked tenon and needs a little cork grease. My Irish flutes are corked and require cork grease on the tuning slides and tenons. I agree on frequent cleaning. The flutes are cleaned daily and the whistles about weekly. Best.