Elvis used vibrato in every song.  He couldn’t do those slow songs with excellent vibrato without practicing, by vocalizing vibrato every day.

Vibrato takes 60% more breath to sing.

Audiences are soothed by vibrato.  Imagine you are soothing the audience while you sing vibrato.

Simple Vibrato

Same as Notes Vocalizing methods but add vibrato to the end of the vowel so it has 3 cycles or more.

Long Vibrato

Same as Notes 5 note Vocalizing methods, but hold the individual note for 8 counts.  Keep the vibrato consistent till the end.

Hard Vibrato

Hold a note using a strong vibrato, typically called a wobble, for 8 counts or beats.  When mastered do the counts to 12.  Then do mezzo forte.   Then forte.  Do this throughout your vocal range when vocalizing.

Vibrato should be practiced while using a metronome (on your phone).  Your vibrato cycles count must be in sync with the beats of the metronome.

Mixed Vibrato

Same as 5 note vocalizing but no vibrato until the 5th note the highest note, then hold that note with vibrato for 4 to 8 counts, then descend with non-vibrato notes.  The last note on the run is a non-vibrato note.  You will want to do vibrato on the last note but control your voice.

Then reverse the exercise.   Have the first 4 notes vibrato notes, and the 5th highest note a straight no-vibrato note.  All other notes are with vibrato.