Requirement: Perform 5 ranks
Base effect: All allies within 30 feet are immune to the staggered and dazed conditions, but cannot benefit from the extra attack granted by haste or similar effects as well. Furthermore, they gain a +1 morale bonus to saving throws against all effects with duration longer than instantaneous. The bonus becomes 1 point higher at 5th level and every 5 levels thereafter (maximum +5 at 20th level).
You grant all allies within 30 feet the ability to attempt a second saving throw against an ongoing effect they are suffering from, such as spells, poisons, diseases, or supernatural abilities. Failure on this extra saving throw has no consequences, while a successful saving throw affects the condition as if the subject had made the original save against it. If an ally is suffering from more than one condition, they choose which one to apply this effect to. If the extra save granted by centering chant against a specific condition fails, additional uses of centering chant from the same siren cannot grant additional saving throws against that same condition.
Weak Refrain: Allies make their saving throw with a –2 penalty.
Intermediate Refrain: Allies make their saving throw without penalties.
Strong refrain: Allies make their saving throw without penalties. Regardless of the result of the saving throw, the chosen effect is suppressed until the end of their next turn.