I remember auditioning a guitarist for the band I was in. He came in, the band played a few songs, he played blindingly fast lead guitar over the top of them ..............so far so fantastic!. I then decided I'd teach him some of the chords so he could play rhythm.
I said, 'This song starts in E'
He said, 'what?'
I said, 'Just play an open E chord'
He said, 'How do you play that?'
He'd spent the last, however many years, learning every Steve Vai solo know to man but couldn't play an open E?
He didn't get the job.