Asked by Bass players? I don’t want to give unwarranted and unqualified advice here.
i’m not a bass player, but i am taking low string tech, and i have a good teacher.
the technique is basically the same as on upper strings— you come from behind the note (with out passing it!) and move your forearm and hand in unison (keeping good posture), starting slow with say, measured eighth notes, then gradually decreasing to sixteenths, thirty seconds, etc., until you have vibrato. similar to the way little kids tend to figure out the jaws theme. (da dun… da dun.. da dun da dun… dadun dadun……dadundadundadundaun…!)
my teacher likes to call this “the wah-wahs” after the sound it makes in the beginning.
[that said, the way i learned vibrato was by watching lots and lots of videos of my favorite performers and analyzing what they did, then practicing what i saw in front of a mirror.
i also observed my peers in this manner. then one summer i decided to play cello and everything made so much more sense— probably because they play with gravity. i can now pull a pretty decent vibrato out of basically any stringed instrument.]
