When does a singer’s vibrato become a wobble? When it becomes unpleasantly wide, so that the note is no longer clearly distinguishable, and the rhythm of the wobble dominates the aural experience. It is very difficult to control the wobble when it has set in, as, like vibrato, it is created by a complex of unconscious muscular responses. All the singer can do is go back to basics with a singing teacher - work on breathing and support and hope for the best.