Just a few photos to explain how to obtain a quite good vibrato following my personal opinions. Surely it will not the best way, but I will try to explain my personal thought.
Let give me a little of time to develope it
"We all must thank you, Dear Vito, for your tireless work for all of us bassists!" You are doing so much for your colleagues and your art.
PIERMARIO MURELLI - "Nuova didattica per contrabbasso " Ed. RICORDI