00:16:25 You're off the beat.
00:16:26 Your orchestra is lapping you.
This is how I see it:
To lap somebody in athletics is to become a full lap of the course in front and therefore pass them again. In your example, the suggestion is that the pianist is so far out of synch with the orchestra that he has fallen well behind the beat, and that the orchestra is, in a sense, now catching him up again from the rear.
not a teacher
Student or Learner