I can’t tell the difference between a note which is sharp and one which is flat but I think I play ok. Does it really matter?
If you play with other people and/or record yourself with accompaniment, I’d say it’s pretty darn important.
Let me ask you this: can you hear if an instrument is out of tune?
Let me ask you this: can you hear if an instrument is out of tune
No, I have to use a tuner. I have noticed I do a fair job of keeping most notes within 15 cents or so of what the tuner says is in tune but I sure don’t hear it.
Not if you don’t care.
When you play an instrument like whistle without fixed intonation (such as, say, accordion), that requires you to bring each pitch into tune as you play … then, yes, unfortunately, lack of pitch discrimination is a problem. You may think your intonation is good, but others will notice. Whether they or you care is a different matter. 
In context, differences of 10 cents or so may be normal and tolerable, depending on the setting (instruments, acoustics, melodic contour of the tune).
Not everyone has the same natural ability, but pitch perception is something that can be improved by training. (Though I’m sorry I can’t name any specific e.g. software trainers offhand.) There’s also an online site that lets you test your pitch discrimination - I’ll try to find the link. As I recall, I tested down to +/- a couple of cents or Hertz, I forget which, under test conditions.
Some whistles … Burke and Overton come to mind … have a remarkably even intonation, and are tolerant of varying breath pressure. So those might be a good choice for someone with pitch challenges. And some whistles definitely require more active pitch control.
Found it, the Adaptive Pitch Test:
http://tonometric.com/adaptivepitch/
I just tested at 1.05 Hz at 500 Hz, or 3.6 cents. I’ll bet some of you can do better.
The other music tests are fun, too, if you have a few minutes to waste.
Boy, 'aint this the truth. I find this everytime I play my violin. I think I’m at correct intonation until I try to play with a recording . . . Oy!!!
I agree in that I have read that Burke whistles are very good for this. Pretty much just blow and you get a good note. This might help the OP in that he will always hear a good note and in time will begin to recognize when the note is sharp or flat.
0.375Hz
(but that hardly means I play in tune).
0.375Hz
(but that hardly means I play in tune).
Same about me, I’m completely out of tune all the time.
You know, it may be more important to question the degree of intonation required to be noticeable. I just ran the tonetest and got a 1.65Hz discrimination. Is this good bad, or what and does it really matter? I mean, how bad do you have to be for poor intonation to be noticeable?
What I am getting at is this: There have been some recent threads showing tuning in cheapie whistles. The software Flutini / Tartini was used and gave a series of error-bars for each note played for a given piece of music. It seemed that for the examples shown in the thread, the whistle did not play each note perfectly in tune all the time, sometimes being off by what looked like quite a bit. So, would an MP3 or live listening to the player/whistle/tune sound terrible? Probably not. In other words, if we gave the best whistler in the world, the most demanding whistle (in terms of breath requirements for perfect intonation), would we notice it? Do the best whistlers keep intonation to within, say 5Hz or whatever? If we listened to the tune, tapped our feet and got emotionally involved with the music, would we notice 1.65Hz or even 5Hz differences in intonation, would it matter?
I suppose what I am saying is that the original poster of the question may be overworrying. BUT… I am by no means an expert on the whistle.
Finally MTGuru…how do you convert between cents and Hz and semitones and cents?
Charlie
1 semitone = 100 cents
c = 1200 * (log(f2/f1)) / log(2)
where f1 = first frequency, f2 = second frequency, c = difference in cents
Or just go here:
http://www.sengpielaudio.com/calculator-centsratio.htm
0.375 Hz @ 500 Hz = 1.3 cents
1.65 Hz @ 500 Hz = 5.7 cents
MTGuru,
Thank-you. I had assumed that cents meant 100ths, but was unsure whether whole-tone or semi-tone.
BUT, 5.7 cents or 1.3 cents may be totally academic, if even the best players do not play to within that degree of intonation. I can’t say that I have ever listened to any whistle pieces and noted anything as out-of-tune as the 1.65 Hz that I was able to distinguish in the intonation test ie. what I can distinguish when listening to two 500 Hz tones is far, finer than what I could notice in a tune being played by anyone.
Charlie
MtGuru, thanks for the link! I am not tone deaf but my pitch perception is not that that good. I had a score of 57.6 HZ apart at 500 HZ. You mentioned that was something that could be improved. What would you recommend?
Same result here. I have an “Exceptional ear”… when it comes to unmodulated sine waves. 
I am sure all this will be useful. Everything can be useful.
However I challenge your statement about “natural ability” about pitch perception following a reference to the fixed intonation of accordions. Equal temperament (as on keyboards) is an artificial thing and hardly the intonation that those with a natural musical ear hear as a good intonation.
It is quite possible for a whistle player to play something that is in tune to his or her ear but that is not in tune with an accordion. Of course an experienced whistle player will tend to automatically and intuitively adjust articulation to be as out of tune as the accordion.
Equal temperament is hardly a measure of natural tuning. It is, in fact, a convenient artifice.
Adherents of just tuning speak as if that temperament is some kind of absolute. Tell me, just or equal temperament or just plain out of tune?
http://www.youtube.com/watch?v=hoYfGy785_s&feature=related
http://www.youtube.com/watch?v=1XLOTnrpJWc&feature=related
http://www.youtube.com/watch?v=Lz6_cnpa8cY&feature=related
http://www.youtube.com/watch?v=DY1pcEtHI_w&feature=related
http://www.youtube.com/watch?v=pKDAbp9m5yw
These all seem “natural” to me (although Eric Dolphy took some getting used to).