How is Alexander Technique different from Pilates or Yoga?
Alexander Technique is not like Pilates in that it does not involve actual exercise (like on the cadillac or reformer) but has some of the same ideas about being centered.
Pilates was developed to strengthen the body core (Pilates originator, Joseph Pilates, was a gymnast who wanted to speed up recovery). Alexander Technique was originally developed for stage performers to "free up" their bodies (Mr. Alexander was an actor). That is, you would not get stiff after an Alexander Technique session like you would after your first Pilates sessions, nor will Alexander Technique do anything for your muscle strength.
Alexander Technique is more about realignment, which is where it comes closer to Yoga. But it does not have the meditative and stretching/relaxing element of Yoga. Alexander Technique is stricly about using your body better and more efficiently.