Harmonic

A harmonic weapon reverberates with a constant, almost distracting hum or makes pleasant twanging noises when moved around. When you strike and deal damage to a creature with a harmonic weapon, the sound it produces finds a harmonic resonance in the creature. Before the beginning of your next turn, any ally that targets this creature with a weapon in the sonic category gains a +2 circumstance bonus to the attack. This weapon fusion can be applied only to weapons that deal sonic damage.