So threads like this probably exist, but I need it for myself. I've been trying to get this down and it sounds terrible. I don't feel like I'm improving at all. Have any of you struggled with thumb position vibrato? I feel like I'm the only one in my studio who can't do it. It's jittery and awful and it pisses me off. Have you experienced this? Did you get past it and find that beautiful sound? I need some advice and moral support, because it's hard to get through any of my practice sessions these days without feeling like I need to drink away the pain.