Same thing is happening to me, just started my PhD in one of the leading robotics labs, and I feel like I don't belong there. It's beginning to cause insomnia and depression, or symptoms of those.
You're there now.
The sooner you do the better.
I had to take a break from my studies because as things got worse, I told myself if I just pushed harder I could get through it on my own. That didn't work out.
Also, with a bit of mental training (say meditative thinking) you can tame some of this effects. I know I now can recognize when my brain take an unnecessary turn and can slow down. It's far from perfect but it helps. Don't think it's unavoidable, get fun time, stop listening to the fears too much.
They chose you.
You belong there if you want to be there.
You have an amazing opportunity, be inspired!
You got this.
it is actually an asymmetric situation clearly more beneficial to you as you do have a meaningful upside here - you can learn from them - while they are "surrounded by only a grad". I feel sorry for them or for any other people in similar situation who is surrounded by me :)
There's a differential equation side to human relationships. It's like pressure equilibrium.
Maybe Kent was too used to be in control, and in these situation you have none. And you need a clear, trusted communication channel to know how to parse things.
The analogy with music sounds odd to me. Music has this property that when done wrong everything falls quickly apart and you will realize it on the spot. If the vibe is still there, then to me you're doing music good enough.
I also think there are two notions being discussed here: feeling like an imposter, and self consciousness (anxiety, overthinking, rehashing things long after).
I wish I could just pat him on the back and tell him not to torture himself. As he said, he didn't get there by accident. I also wonder if he talked with colleagues at his jobs, or people in the field before writing this.