When a vocalist "scats," what do they use for the words?

When a vocalist scats, he or she uses meaningless or nonsense syllables for "words".

Scatting serves the purpose of enabling a vocalist to improvise melodies and rhythms using his or her voice itself rather than instruments. For instance, if a vocalist imitates the sound of an electric guitar riff using meaningless syllables such "na" "wa" or "ha" it is an example of scatting.