[cjhveal]

It seems obvious, even to those unfamiliar with phonetics, how tonal languages are transformed into whistled languages by whistling the underlying tone contours.

However, even languages with no phonemic tonality are able to be whistled because we distinguish vowels almost entirely by the volume of the harmonic frequencies produced by changing the shape of the resonating chamber of the mouth. Musicians often call this "color" or "timbre". Jaw aperture roughly corresponds to the volume of the first formant produced, and how the tongue is raised or retracted within the mouth roughly corresponds to the second formant produced.

Even the surrounding consonants leave their mark on the surrounding vowels. For instance, sounds produced with the lips, (like English "b"/"p"), tend to lower the formants of the surrounding vowels. Consonants produced with the back of the tongue against the soft palate (c.f. English "k"/"g") tend to "pinch" the second and third formants of the preceding vowel closer together. Collapsing and merging consonant clusters while bringing the tonal variation into the fundamental pitch is one of the most common theories of tonogenesis, or how tonality evolves in languages.

Whistled languages based on non-tonal languages tend to whistle the patterns of the second formant, which captures subtle information about what the vowel and surrounding consonants would have been in the underlying spoken language.