Scholars believe that the Siren's Gift is usually unrecognized on the Major Cloud-Islands because the knowing combination of Giftedness and musical talent is rare.
Sirens' abilities are reflective of their targets: the more intelligent the target, the easier the mystical effect. Most sirens can easily affect a human, but it seems to take more power or skill to affect an animal. Only the most puissant sirens can affect unliving materials (doors, wood, rock) or abstract concepts (time, luck) with their Gift. (It is said that the most advanced practicioner of this Gift, Nalsa actually sung a material object into being, but information on this event is sketchy.)
Those with the Gift of the Siren use their songs to influence the thoughts, emotions, and motivations of their audience. They can divine knowledge about a person (emotions, present state, and destiny) by listening to that person sing. They all have perfect pitch. They claim to be able to access "the music of the sphere" to enact other vague effects.
Sirens that cannot control their emotions inadvertently tend to cause people and animals around them to act in accordance to the emotional state or goals of the last song they sang aloud.
Those with the Gift of the Siren are usually treated as though they had the Gift of the Manticore (not a good situation!).