Even the damned souls of Stygia need a little music. 

You feel compelled to play pranks. When this weapon does the maximum possible damage to a hostile creature, it must make a Wisdom check against your spell save DC or be instantly Charmed by you for one minute. Further damage done to the creature instantly breaks the effect.

Two-handed, range 20, 2d6 Psychic damage, attack rolls use Accordion proficiency and Charisma bonus. 

Notes: Damage: Psychic, Cursed, bard, Damage, Combat, Cursed, Instrument