If a singer is only able to vibrato at particular pitches or on certain vowels a sign that vibrato is being produce incorrectly, such as a vocal wobble?
For example if someone who is new to vibrato is only able to produce it on lower notes, could this be a sign the vibrato isn't coming from the right place?
If you can't do proper vibrato at higher pitches it's probably down to improper breath control. Make sure you can very comfortably hit the higher notes without straining before attempting anything fancy like vibrato. Also, make sure you are producing the notes properly as well as breathing correctly - the high notes should be coming from the same place as the low ones, and shouldn't be forced out. Remember to sing from your diaphragm.
If you can hit these notes comfortably, your issue is probably your technique. If this is the case there are many online resources to teach proper vibrato technique, from paid resources to WikiHow articles.
Of course there are multiple ways to artificially create vibrato. The most interesting example of this to me is what Jonny Hawkins from the band Nothing More does, where he kind of vibrates his fingers against his throat. See here for an example. Make sure you don't hurt yourself though and study up on it properly...
