Det är precis vad texten på Combat Style Master säger:
You can switch your style as a free action. At the start of combat, pick one of your styles. You start the combat in that style, even in the surprise round.
På definitionen av en fri åtgärd :
Free actions consume a very small amount of time and effort. You can perform one or more free actions while taking another action normally.
Observera att antalet tillgängliga tillgängliga åtgärder begränsas av din GM.
However, there are reasonable limits on what you can really do for free, as decided by the GM.