If Relaxation is the foundation and Sense Memory is the structure of the "house of method", then Concentration is the mortar that fuses the structure to the foundation.  Without extremely developed powers of concentration, nothing you do as an actor will have much substance.

"Stage fright" properly should  be termed "Audience fright", because that's what it is.  When the actor becomes aware that he is being observed by "them", "out there", tension finds its way into the actor's life on the stage.  The key word here is "aware".  The actor must first become aware of being observed before the observers can cause the actor  to suffer that state of self-consciousness known as stage fright.

So the "trick" here is not allowing oneself to become aware of the audience.   For the actor, that means concentrating on a specific object.  If you are concentrated fully on a specific object, it is impossible to be concentrated on the audience.

On what does the actor concentrate?   The actor concentrates on an object.  On which object does an actor concentrate?  Ideally, the actor concentrates on an object that is suggested from the logic of the play.  But this is not always the case, nor is it always necessary.  A simple test proves this again and again in my workshop.

Two actors are having difficulty overcoming a problem in a scene.  The problem is usually one resulting from the actors' lack of concentration on a specific object. 

As an exercise, I will separate the actors, and give each something upon which to concentrate, without letting the other know what this "object of attention" is.  I might tell Actor A to multiply the numbers 385 and 269 in his head while working the scene, and give me an answer by the end of the scene.  For Actor B, I will simply require that he concentrate on his partner, and try to make sure his partner is really listening to him.

The result of this simple, common exercise can be startling. 

The actor doing the multiplication is suddenly very concentrated, seemingly involved in deep thought -- and here's the catch -- even though he is not concentrating on something that has anything to do with the play, he nevertheless appears as though he is involved in the life of the play.  He seems very real.  And he is really thinking on the stage.  Not just saying his lines on cue.

Now, faced with Actor A in a concentrated state, Actor B finds his work in the scene has taken  a quite different turn.  Now he has something to do, and depending upon the amount of concentration Actor A is able to command to achieve his task onstage, Actor B will have no choice other than making a sincere effort to communicate with Actor A.

When this happens, neither actor is aware of the audience,  but what the audience perceives at this point is two real people trying to accomplish whatever it is that concerns them in their life on the stage.

THE CIRCLE OF LIGHTS

Stanislavski developed a powerful exercise for his students to help them better understand and implement the use of concentration on the stage.

Arranging the stage lights in a wide circle, he would ask the actor to concentrate only on the props and set defined within the circle.  As the actor became comfortable with this "boundary", the circle of lights would be reduced in diameter, while props and set would remain in place.

Ultimately, the circle would include only the immediate area of space in which the actor was standing, and the actor at this point was asked to concentrate only on whatever he could use on the stage within this limited area.  The exercise was invaluable in helping the actor focus his concentration more specifically to an object of attention.

Another exercise which is very useful for eliminating awareness of the audience is the creation of the "fourth wall" on the stage.  Originally designed for use on a proscenium stage, which is bounded by three "walls", the actor was to sensorally create the "fourth wall" while looking in the direction of the audience.  This " fourth wall" could be a recreation of a wall from the actor's own life, e.g.  a bedroom, living room or office, etc., with the actor, during rehearsal or in the workshop or studio, taking whatever time necessary to faithfully create the wall. 

Obviously, if the actor "sees" a "real" wall where the open space of the proscenium arch actually exists, his awareness of the audience will be eliminated.

This technique works as well in situations where the stage has more than one area open to the audience.  It is then simply a matter of creating more "walls".

I have told you that the Relaxation Exercise and the Sense Memory Exercise help develop the actor's powers of concentration.  I assume that, after a period of  practice, you have become proficient with relaxation and the creation of sensory objects on the stage.  Now how do you get to those difficult moments in the scene where it becomes obvious that who you are representing in the story is going through an extremely difficult emotional experience?

There are many ways to achieve true expression of emotion onstage.  Based on what we have learned up to this point, we would choose an object that has a personal association for us, which we have tested for reliability in the workshop  (and know that by concentrating on the sensory elements of this object we will produce a desired emotional response), then we would commit our full attention to the object without concern that the emotion we desire will appear.

This is the most difficult part of using objects to produce emotions.  You've tried it in the workshop and at home.  It works consistently.   But in the performance of the scene, it fails.  Why?

Because you wanted it to work, it didn't work.  The lesson here is that you must never go for the emotion, only for the associated stimuli that have in the past helped produce the emotion.  In other words, make the effort to create the sensory stimuli associated with the object of your attention without being at all concerned with the results of this effort.

You cannot "will" emotions.  In life, emotions are produced of their own accord as a result of certain stimuli which affect the human organism.  It is the stimuli upon which you work to recreate, as you did in the workshop, when the audience was not there to "pressure" you to "perform".