Through immersion in the vibrations of sound waves put out by your song voice, you've figured out how to nullify the sound waves from other sources. Any spell whose effects are based on sound can be nullified. For example, the spells Cacophony, Suggest, and Thunder, as well as any spell cast using Spellsong. Make a Perform check against the Casting Roll from the source of the sound. If you succeed, any harmful effects to you or other creatures are completely negated.