Reveler's Concertina

While holding this concertina, you gain a +2 bonus to the saving throw DC of your bard spells. As an action, you can use the concertina to cast Otto's irresistible dance from the item. This property of the concertina can't be used again until the next dawn.
See the Tool Proficiencies entry for more information.
Proficiency with a musical instrument indicates you are familiar with the techniques used to play it. You also have knowledge of some songs commonly performed with that instrument. History. Your expertise aids you in recalling lore related to your instrument. Performance. Your ability to put on a good show is improved when you incorporate an instrument into your act. Compose a Tune. As part of a long rest, you can compose a new tune and lyrics for your instrument. You might use this ability to impress a noble or spread scandalous rumors with a catchy tune. Musical Instrument Activity DC Identify a tune 10 Improvise a tune 20

Rarity

Wondrous item, instrument, rare (requires attunement by a bard)