Blocky bards is a mod that mainly adds 1 new item, the lyre. When pressing the Y key, you can swap between helpful mode and harmful mode. Helpful mode heals any nearby players, pets or allays. Harmful mode damages any nearby hostiles.
Alongside this, there's a decorative bard hat you can wear, and a special lyre enchantment, StunStrum, which adds a chance to stun an enemy when in harmful mode.