Hello,
 
Is there any way of approximating a human whistle with software?  I miss whistling.

Start with a sine or filtered triangle wave, add some vibrato, and a noise envelope to simulate the blowing.
There is a short buildup to getting the sound started and the resonance forms in the mouth and there is also some pitch modulations as one blows harder and softer.
 
This could be simple, or really complex if you want a lot of accuracy.
 
Massive has a patch called 'The Whistler' - it is just so-so.
Dimension Pro has one in the DSF Planet Earth set, only so-so.
 
I tried to search for more, but most are the physical whistles, bird calls, and flute like sounds.

I've never found a truly realistic one. Fortunately, it's a really cheap instrument! Do you have a microphone? 

Realitone's Realiwhistle is pretty good. It's a tad bit noisy on its own, in my opinion, but works well in a mix if you have some supporting instruments and use some EQ to clean it up a bit. It's on sale right now for $24.95 (Mother's Day speicial, down from $39). 

http://realitone.com/realiwhistle/

That one doesn't seem too bad. Still a bit artificial but you might get away with it in a mix.
EDIT: I mainly hear some zipper noise on his legato notes, but perhaps that's better if it's set to a longer time.

These are probably the best whistle sample libraries at the moment...
* https://www.vsl.co.at/en/Voices_Complete/Vienna_Whistler
* http://www.bestservice.de/en/whistler.html
 
Scott

--
Scott R. Garrigus - http://www.garrigus.com
* Cakewalk SONAR Video Tutorials: https://www.youtube.com/u...gus?sub_confirmation=1
* Author of the Cakewalk Sonar and Sony Sound Forge Power book series: http://garrigus.com/?PowerBooks
* Publisher of the DigiFreq music recording newsletter: http://www.digifreq.com/
* Publisher of the NewTechReview consumer tech newsletter: http://www.newtechreview.com/

Sanderxpander
I've never found a truly realistic one. Fortunately, it's a really cheap instrument! Do you have a microphone? 

Droll! Sometimes I find my lovely wife checking the weather on-line when she's by a window.

thanks for all the suggestions.  To my ear the vienna might be worth the money, however it's always nice to save some dough if I can.

TTS has one IMO it sounds very good.

Is there nothing TTS can't do?