Someone who doesn't know all the lyrics to a song might sing "la la la" or "dum dum dum" in place of the verses they don't know. Is there a verb for this? Similar to "humming" the tune, but with syllables?
I'm aware of the verb "scat," but to me it implies a particular style of fast-paced jazz nonsense vocalization. I'm looking for a more general word, if it exists.