Boon of Revelry

Boon of Revelry
Feat
Prerequisite: Level 19

You gain the following benefits.
Inspire Dance.
You always have the Otto's Irresistible Dance spell prepared. You can cast it once without a spell slot, and you regain the ability to cast it that way when you finish a Long Rest. You can also cast the spell using any spell slots you have of the appropriate level.
When you cast the spell, it requires no spell components, and taking damage doesn't break your Concentration on it.
Sing Out.
While a creature that failed its saving throw against your Otto's Irresistible Dance has the Charmed condition from that spell, it can't cast spells with Verbal components, and it sings delightful nonsense if it can sing.

Source: Forgotten Realms: Heroes of Faerûn (FRHoF), page 43