Regarding Vibrato Techniques

Hey all,

Maybe someone out there can share a best practices tidbit on how they practice their vibrato:

I feel that when I add vibrato to a sustained note, it comes out very staccato-y (choppy each note separate from the other). I would like my vibrato to have a bit more of a legato feel (all notes flow together), since when I hear the material I'm practicing, the vibrato is more of the latter. 

Any thoughts on how - or what - to practice to achieve more flow on a vibrato?

G~