You play the most jarring, abysmal song that could ever be played. As a bard whose words echo the power of creation, you are taking your song sheet and reversing it, causing the power of destruction instead. You may continue this song by using your bonus action on it every turn. Every turn that this spell is cast, all creatures in a 30 square feet roll a Charisma save or take 2d6 Necrotic damage and stumble 5 feet away. All Undead take 3d6 Radiant Damage instead.

Essentially you are playing death metal