vocable

puhuttu sana puhekieltä A word or utterance, especially with reference to its form rather than its meaning.
1974, Anthony Burgess, The Clockwork Testament:

Without words and almost with the seriousness of asylum nurses they at once set upon an unsavoury-looking matron who began to cry out Mediterranean vocables of distress.

At first the man puzzled; then he smiled. He pronounced a string of uncouth vocables.

Many Native American songs employ vocables, syllables that do not have referential meaning. These may be used to frame words or may be inserted among them; in some cases, they constitute the entire song text.

a vocable marker, a vocable thing