Vibrato results involuntarily from a balanced and consistent amount of air pressure, and is basically a muscle spasm similar to what happens when you hold something heavy for a while. It is normal and healthy, and if you are singing well, it should result without any additional effort on your part.
Is vibrato natural or learned?
Vibrato is something that happens very naturally when your vocal technique is solid. Particularly when your voice is creating sound with a lot of freedom. But it is also a skill that can be learned. ... Use these exercises to begin creating singing vibrato.
Does vibrato happen by itself?
When the voice is free and the student is relaxed, vibrato will appear spontaneously. ... When good tone production, resonance, placement of sound, breath management, as well as relaxation, are in place, vibrato naturally results, or naturally occurs, in the singing voice.