Insidious Rhythm

Enchantment (Compulsion)
Level: Bard 1
Components: V, S
Casting Time: 1 immediate action
Range: Medium (100 ft. + 10 ft./level)
Target: One creature
Duration: 1 minute/level
Saving Throw: Will negates
Spell Resistance: Yes
You recite a foolhardy ditty, tapping your foot in time. With a wink and a grin you mark your target, who shortly thereafter follows suit.
The subject takes a –4 penalty on Intelligence-based skill checks and Concentration checks due to an endlessly recycling melody stuck in its mind. Whenever the subject attempts to cast, concentrate on, or direct a spell, it must succeed on a Concentration check (DC equal to insidious rhythm’s save DC + spell’s level) or fail at the attempt.