How to Whistle a Language

Turkish has a lot more vowels than Spanish does but it also has vowel harmony rules which actually cuts down on the number of distinctive vowels that could occur in any particular slot. So they so whistled Turkish gets away with having three relative vowel frequencies in its whistled mode. The maximum number of distinct vowels that you can maintain for perceptual purposes is probably like four or maybe five. And one of those might end up being a schwa which is another feature of whistled Turkish. There are three distinct perceptually distinct bands for specific vowels but there's also a schwa vowel whose range overlaps all of the others.