Young vocal improvisers are always concerned about what syllables they should use – in fact, I think they’re sometimes more concerned with that than with the ideas of improvising melodies! That concern often leads to some pretty extravagant syllabic choices: lots “squee” and “skadoodle” and “skiddama” types of things.
To them I say, simplify. Here are a couple good rules of thumb for starting out.
- Use the kinds of syllables you would use when singing along with a song you love but forgot the words to.
- Choose b and d as initial consonants most of the time.
- Think baby talk. What sounds would a 6- or 9-month old make?
You can definitely expand outwards from these as you become more confident, and that can be informed by listening to the long tradition. But using these rules will get you feeling more idiomatic right away.