User blog comment:Mihaelandnate/The chronicles of mihaelandnate's failures with VOCALOID- vibrato edition!/@comment-24684900-20140505005304

Oh, there can never be too much vibrato. Though seriously, it's more on style then anything. So if it's operatic go crazy with vibrato, if it's pop not much vibrato. Though thing to do to keep Vocaloids from sounding flat is even if you want to have the Vocaloid sing a long note straight, put vibrato on it. It doesn't have to be a real noticeable vibrato, but it'll do wonders. Anything else would be probably from listening to other people, or singing it yourself. That'll give you a general guide on where to place vibrato.