Scat Text

Rhythm is indicated using long and short vowels and open and closed syllables as in classical scansion (iambs, cretics, etc.)

Pitch is the funky bit; the vowel sounds are used to suggest not pitch itself but an approximation to the first derivative of pitch. Front vowels, expecially un-rounded front vowels (e.g., 'ee'), suggest rising pitch. Back vowels, especially rounded back vowels (e.g., 'oo'), suggest falling pitch.

Consonants are then available for free semantic play, except that they sometimes affect the scansion by closing a syllable. You can hide actual meaning, or at least hints of it, among the consonants. Finding such meaning would be a bit like reading classical Hebrew where, I'm told, vowels are only marked as an afterthought.