The entire reason that Alexander Technique exists today is because its founder, F.M. Alexander was an actor who developed hoarseness when performing on stage. Through years of self-study he was able to figure out and inhibit bad habits that caused his hoarseness.

The development of self-awareness that is a necessary part of the Alexander Technique is immeasurably beneficial to the actor. When acting in front of a live audience there is so much stimuli relating to the audience and its reactions that actors may not remember critical information about their performances. Alexander Technique encourages actors to stay with themselves from moment to moment so they are better able to evaluate their performances. For example, if they hear tightness in their voice, they can try to discover how they are misusing themselves. 

As a result of Alexander Technique lessons, actors can gain an intimate knowledge of how they use their bodies, which is very advantageous when creating characters they want to embody physically at will. 

When actors can inhibit their interference with the proper lengthening of their head-neck-back relationship, their voices have more power and resonance, which can result in greater stage presence. 

Wider emotional expression is available to actors more readily when they can free themselves of harmful, constraining muscular habits. With the poise and nuance they gain with Alexander Technique, actors can be open and responsive to other actors in the ensemble and access genuine emotional vulnerability and truth in their performances.