Hindering Song

Deafening Song (EL) , Perform 27 ranks, bardic music class feature,

You can use song or poetics to hinder enemy spellcasters within a 30-foot spread from you. To successfully cast a spell within this area, a spellcaster must make a Concentration check as if she were casting defensively, and all such checks have a penalty equal to half your level. You can choose to exclude any characters from this effect (usually your allies). You may sing, play, or recite a hindering song while taking other mundane actions, but not magical ones (see the bard's inspire courage ability for more details). You may keep up the hindering song for a maximum of 10 rounds. Using the hindering song counts as one of your uses of song or poetics for the day.

You can use song or poetics to hinder enemy spellcasters within a 30-foot spread from you. To successfully cast a spell within this area, a spellcaster must make a Concentration check as if she were casting defensively, and all such checks have a penalty equal to half your level. You can choose to exclude any characters from this effect (usually your allies). You may sing, play, or recite a hindering song while taking other mundane actions, but not magical ones (see the bard’s inspire courage ability for more details). You may keep up the hindering song for a maximum of 10 rounds. Using the hindering song counts as one of your uses of song or poetics for the day.

Your bardic music interferes with opposing spellcasters.