Have you heard the phrase, "You can set a watch by his performance"? It's used in theater to describe an actor whose timing is so consistent night after night, right down to smallest hand gesture, that you could probably set a watch by his performance.
I first heard the phrase years ago on my first show as an Equity Stage Manager, Shaker Heights. One of the supporting actresses turned in such a performance. I didn't even have to watch her to know exactly what she would do next.
In my limited experience, I have found that it is mostly supporting characters that are so consistent. Once the actor has discovered the essence of the character, there are not many outside forces that alter that character's path.
Actors in leading roles tend to have more stage time and therefore more contact with the other characters in the play as well as the audience. In addition, leading roles have stronger emotional arcs as they are the ones driving the dramatic action of the play. Given that, it is easy to see how a performance might be influenced by the mood of the actor or the rest of the cast or even the audience.
For example, during Piano Lesson, Brian Anthony Wilson played Avery, a supporting character. You could definitely set a watch by his performance. During each show, I would watch for him to take off his hat and bend down to whisper in Berneice's ear. It happened the exact same way every night and it fascinated me, this precise timing. Having only worked with Mr. Wilson in this one play, I'm not sure if he would do the same thing if he had a leading role. Luckily, he's a great actor and well-loved by Philadelphia audiences so I hope I get the chance to find out. Now, another thought just occurred to me, Mr. Wilson also works in film which requires an actor to turn in the same performance take after take. I wonder if this informs his stage acting?
During Piano Lesson, I also worked with Kes Khemnu (who incidentally, is on stage right now at the Arden in Gee's Bend) who played Boy Willie, the lead in the show. I loved watching Mr. Khemnu for the opposite reason of Mr. Wilson. Mr. Khemnu truly played off the emotions of the rest of the cast as well as the audience. His performance, while consistently amazing, changed slightly (and sometimes more than slightly) with each show. It's not he altered his blocking drastically, it's that his gestures or the height of his emotional state changed as he reacted to his own mood or the mood of the cast or even the audience.
Anyway, I've been thinking about this while watching Candide because you could really set a watch by everyone in the cast; they are so exact night after night. Part of it has to do with the fact that it is a musical but also I think it has to do with the show itself. The show is huge, it's performed in the round with chalk and mops and boxes. In order to get through it without a misstep ("do I chalk here or move a box?") or without crashing into another cast member, the movements have to be precise. And even within little scenes where the actors have some wiggle room, there is very little deviation.
But don't get me wrong, it's not monotonous at all. It's great fun to watch, especially since the performances are so good and I marvel at how much energy each actor brings to the stage, show after show. I guess I'm getting a bit nostalgic since this is the last week of the show. It's rather like watching your favorite movie over and over again; only this movie won't be playing next week.